Now this doesn't mean the other two reasons don't apply. They do. But they always seem to morph into number two or someone stops playing the clone. If you're a bit lost check my previous blog post.
If you start with a clone because it's all there is or it's convenient, one of two things will happen. Either you will end up going to the original sources eventually anyway, or you will end up preferring the newer "clone" version. Hence you are playing for reasons #2. And if you are designing for 1e but playtesting in say OSRIC so you can actually publish your work then you really think 1e is preferable; it's just that OSRIC allows you to have a testbed. If you are writing for OSRIC because that's what you play, you obviously prefer OSRIC. Hence #2 holds the day again.
So, the only reason to consistently play a retro-clone is because the rules are preferable to what came before. Because you like the flavor of that version. This could be due to organization, presentation, writing style, art, or slight rule changes and fixes that correct previous problems. No retro clone is actually a clone. They can't be by law. There're some slight differences and the differences are significant enough to not be able to seamlessly play with original rules and clone rules side by side.
Devotees of original system rules, wether 0e. 1e, B/X, 2e, BECMI or what have you either prefer to play with the rules as originally written or they convert over to a clone. And there's nothing at all wrong with that. Clones are a step forward in game design from what was. If nothing else in presentation and organization. But if you prefer original rules the clones will never quite do. They are not the same and many fanboys and girls demand the game they used to play, without outside tweaks. However, there is a growing fanbase following of retro clone players too.
I frankly don't even like the term retro clone anymore. As said, they aren't really clones. They are something new and original in their own right. ADD Grognard said it best when he defined the OSR game design movement as 'gamers creating games they like to play'. And some of them are very good and very original. And no, I don't really have a problem if somebody is playing Labyrinth Lord and says they are playing B/X. They can call it what they want. I prefer that they call it what it is however. Why not proudly proclaim that you play Labyrinth Lord, or OSRIC, or Dark Dungeons? I mean it does two things for us. It clarifies our terms and it also gives these old school games a shot in the arm. It gets their names out there more. If everyone who was playing some version of B/X only ever said it was B/X we would hear alot less of LL, BFRPG and others.
Play them because you love them for what they are: better, or at least more preferable, than the originals. There's nothing wrong with that. To tell you truth this is what drove me away from OSRIC. It wasn't my game, which was decidedly 1e. There was simply nothing else that would do. I mean sure I use OSRIC products like Advanced Adventures and First Edition Fantasy, but I run them strict 1e. At least I prefer to. What I'm understanding is that few people want to play OOP games very avidly. At least in my community where gaming is limited at best. And fewer still want to invest in buying lots of OOP products. Believe it or not for them OSRIC is better. They actually prefer it to my 1e rulebooks. And thus my situation is one wherein I find myself looking for a game that I and my players can be happy with.
So, there you have it. ... unless of course you're playing an inferior (for you) game 'cause there's nothing else to play; or it's what everyone else wants to play. We've all been there. We are talking about an ideal world here.