Hardcore gamers are, by their nature, collectors. They want to buy new stuff, particularly new RPGs. Yet, RPGs (as opposed to supplements) are really punishing to the collector. It takes a while to read and digest a modern RPG, much less play it.
In contrast, you can read the typical indie RPG in less than an evening and play it the next night. In that 3 or 4 hour session, you can experience everything that's cool about the game. Next month or week, you can pull out a new indie title and repeat the process.
I think this is part of the reason why RPG mid-tier publishers have been hammered in the past few years. The collector/reader/experimenter end of the market, the guys who buy lots and lots of new games, are much better served by the indie end of the market. They get a lot more enjoyment out of those games, since they can actually play them and get all the cool bits out of them, in a few sessions.