First, allow me to quote a current media sensation, the famed George, R.R. Martin. In an interview with Edge magazine, George explains the following on why so many of his main characters die.
"I think a writer, even a fantasy writer, has an obligation to tell the truth and the truth is, as we say in Game of Thrones, all men must die," ... "You can’t write about war and violence without having death. If you want to be honest it should affect your main characters. We’ve all read this story a million times when a bunch of heroes set out on adventure and it’s the hero and his best friend and his girlfriend and they go through amazing hair-raising adventures and none of them die. The only ones who die are extras. That’s such a cheat. It doesn’t happen that way. They go into battle and their best friend dies or they get horribly wounded. They lose their leg or death comes at them unexpectedly."
As D&D matured it became increasingly influenced by two media, movies and video games. In both these media the main characters rarely die, and if they do in the case of video games, they simply restart, usually only a little behind where they were before. Yes, I'm aware that D&D largely started the current video game craze, but there was an increasing feedback loop between the two throughout the 90's and 2000's viz, 4e and World of Warcraft. I think we can also refer to the red shirt phenomena on Start Trek to affirm the other fact that Martin is referring to here as well,
Sort of like D&D NPCs? We might as well put red shirts on the all of the supporting cast in any D&D campaign for the rate they die compared to PCs.
Martin goes on in the same interview to say.
"Once you’ve accepted that you have to include death then you should be honest about death and indicate it can strike down anybody at any time," ... "You don’t get to live forever just because you are a cute kid or the hero’s best friend or the hero. Sometimes the hero dies, at least in my books. I love all my characters so it’s always hard to kill them but I know it has to be done. I tend to think I don’t kill them. The other characters kill ‘em. I shift off all blame from myself."
Which touches on the next thing that can make a DM reluctant to have a Zero is Death mechanic in their game: guilt. The fact is, we represent every non player force in the world and these forces are what usually spell the end of a PCs life if anything will. And thus by default it must be the DM that killed the PC. This logic, for the religious, makes God responsible for every death in our world--sadly some believe just that. But deeper thinkers have come to the conclusion that if God, or something like God, exists he doesn't control every force in the universe, as much as all things are given free will and the forces of the Universe obey natural law. God may have "created" natural law (or not), but he doesn't control it. DMs are called judges in early D&D for a good reason. They are judging the effects of the laws and mechanics of the game and the situations in which the characters, by free will enter. No, I am not trying to equate DMs with God, only to provide an analogy by which DMs can avoid the guilt they feel when a character dies. There is no need to feel like you killed a character, but that the world in which they play a very dangerous game of "war and violence" has killed them.
So, if we are to assume that characters have free will and that they are engaging in a very dangerous world in which living fire breathing dragons the size of semi-truck & trailers, or larger, fly around the world along with thousands of other evil, deadly beasts roam the lands, then premature death should be a constant in this world. In fact, if you think about the closest analog to the D&D world we have, our world during the medieval age, the picture becomes very clear. In the middle ages, men fought against men constantly. Hence the need for castles, fortified cities and the like. Include death, disease, famine, lack of adequate medical care and the death rate becomes very high indeed. Now, drop in several hundred species, some numbering in the tens of thousands, whose sole desire is not just to conquer but to tear, rend, destroy and kill all in their path. Such critters like goblins, orcs, gnolls, hobgoblins, kobolds, and the like. Add a few serious beasties equivalent to natural disasters, like Dragons, a Tarasque, Basilisks, and Wyverns, and you've got a world hundreds of times more dangerous than our own medieval world. And we know that in our medieval world people died frequently and in great numbers. Doesn't it seem likely that death should be a more clear and present danger in the lives of adventurers than modern games make it?
If we extend this metaphor of fantastic naturalism two other facts quickly jump out. First, magic becomes much more important than even we may assume. Magic is the one force that perhaps can equalize the forces of men against such unnatural darkness in the world. The obvious difference between the forces of good and the forces of evil are, generally speaking, that the evil races are more stupid--humanoid races, or fewer in number--dragons, than humans and demihumans and therefore the good races bring their intelligence and wisdom to bear on these forces in the forms of Clerics and Magic Users. Few are the forces of evil that can generate an evil mage of sufficiently high enough level to truly threaten the civilizations of men long enough to cause them to crumble. The exception are races like the drow, who prefer to stay underground due to inherent limitations, races like the Githyanki, who need physical realms only for raising children and pirating etc.
However, magic being what it is, if unrestrained could rocket our analog middle age into a science fantasy utopia (or at least a highly advanced dystopia--e.g. Eberron) were it not for the ever present pressure of these destructive forces in the world. Certainly kings and emperors could fund the research of advanced guilds and orders of mages to investigate new magical findings that might indeed change the world. And such endeavors, I think, would be a constant occupation in many more established kingdoms. However, the forces of evil constantly tax the resources of the state. From within and without these chaotic dangers of misrule would tax even the most capable of magical societies to simply keep destruction at bay warding boundaries and borderlands, scrying upon their movements and counterspelling whatever attempts these unbalanced, invading forces are executing upon the realms of peace and light.
Thus we can see, our beloved fantasy world stays in a sort of evolutionary stasis, never quite advancing but never quite collapsing. Or better said constantly waning and waxing with the incoming tides of evil and destruction. And, in fact, most fantasy worlds are littered with the ruins of past empires self immolated on the pyre of advancing magic or imploding due to the pressures of encroaching evil. This is good for us who, in game terms, are looking for a fantasy world to play in forever and Peter-Pan like never grow old. But bad, very bad, for those who live there. What I mean is that death would be an ever present constant in such a world, and the danger present there should be reflected in our "play" therein.
Not to forget the divine forces at work in such a world. These divinities take sides in this constant battle, some less so than others given the druthers of the DM. Think for a moment on this: that we play in a world where almost infinitely powerful beings exist and influence the life and destiny on this world on both sides of the battle. There are Gods of the orcs, just as there are Gods of men. Evil Gods, Chaotic Gods, Gods of hearth and home, and Gods of war and strife. Sometimes we in our world, so conditioned by monotheism (whether we are believers or not) forget what true literal polytheism implies. The struggle is real, not just on our fantasy world, but in the realms beyond them acting out the struggle in the Heavens and the Hells just as they are acted out upon our fantasy home world. These forces too, struggle in an endless tug of war for political influence and the fate of not just the world but existence itself. This too, keeps things in a perpetual state of balance, life and death, good and evil, law and chaos.
Now, having said all that and made the argument for the Zero is Death mechanic, I step to the other side. Stories of Hercules, Odysseus, Achilles, Krishna, Gilgamesh, Thor, Robin Hood, Merlin and King Arthur all require one thing: immortality. Even those heroes that in the end die, die with the legacy and promise of a second coming greater than the first. If these are the types of heroes we wish to play, and the types of stories we wish to tell, then by all means, remove the Zero is Death mechanic. In fact, it is better to remove death as a possibility at all. There may be challenges that seem to threaten death, but in the end the hero carries on. But keep in mind, the one thing that all of these heroes also had in common was an unnatural origin. They were not normal to begin with (with the exception of RH). Their births were the products of the Gods, or at the least of strongly magical origins and their destinies fated from birth. Such heroes were never normal men and thus destined for lives that were beyond the normal.
Does this mean that all characters in a Zero is Death campaign die? No, at least not necessarily in battle. Allow me to paint the picture of Conan the Barbarian. Conan was never a hero, at least not by the strict definition of the term. He was a mighty adventurer indeed, but no "hero". Great though he was, in most D&D representations Conan is around sixth to ninth level. Yep, not 20th or 30th not even 15th (admittedly in CB1 & 2 Conan is portrayed as a 13th level fighter and 7th level thief so he is a bit higher there) , but in general not ungodly in level. And moreover the arc of Conan's life is one of random adventuring where he overcomes regional or local menaces--not world shattering epic threats. And he eventually, around say level 9 or so, establishes himself as King of Aquilonia. Effectively this is the equivalent of a 9th level AD&D fighter establishing a stronghold. He then leaves to eventually face death itself. And with the "Death Song of Conan the Cimmerian", I would like to leave this post. Its stanzas speak of the life Conan led, and the stories I would like to tell in my fantasy world of adventure ...
The Death Song of Conan the Cimmerian
The road was long and the road was hard,
And the sky was cold and grey:
The dead white moon was a frozen shard
In the dim dawn of day:
But thief and harlot, king and guard
Warrior, wizard, knave and bard
Rode with me all the way.
The wind was sharp as a whetted knife
As it blew from the wet salt seas;
The storm wind stirred to a ghostly life
The gaunt black skeletal trees:
But I drank the foaming wine of life
Wine of plunder and lust and strife
Down to the bitter lees.
A boy, from the savage north I came
To cities of silk and sin.
With torch and steel, in blood and flame,
I won what a man may win:
Aye, gambled and won at the Devil's game
Splendor and glory and glittering flame
And mocked at Death's skull-grin.
And there were foemen to fight and slay
And friends to love and trust:
And crowns to conquer and toss away
And lips to taste with lust:
And songs to keep black nights at bay
And wine to swill to the break of day
What matter the end be dust?
I've won my share of your gems and gold
They crumble into clods:
I've gorged on the best that life can hold:
And the Devil take the odds:
The grave is deep and the night is cold
The world's a skull-full of stinking mould
And I laugh at your little gods!
The lean road slunk through a blasted land
Where the earth was parched and black.
But we were a merry, jesting band
Who asked no easier track:
Rogue and reaver and firebrand
And life rode laughing at my right hand
And Death rode at my back.
The road was dusty and harsh and long
Crom, but a man gets dry!
I'm old and weary and Death is strong
But flesh was born to die:
Hai, Gods! But it was a merry throng
Rode at my side with jest and song
Under an empty sky.
I've heard fat, cunning priestlings tell
How damned souls writhe and moan:
That paradise they can buy and sell
For gold and gold alone:
To the flames with scripture and priest as well
I'll stride down the scarlet throat of hell
And dice for the Devil's throne!
I faced life boldly and unafraid
Should I flinch as Death draws near?
Life's but a game Death and I have played
Many a wearisome year:
Hai! to the gallant friends I made
Slave and swordsman and lissome maid
I begrudge no foot of the road I strayed
The road which endeth HERE!
~ Lin Carter ~