I feel that the hype machine for gaming is much more powerful than what it is for movies or books. It's really hard sometimes when a big game launch to go through forums like this and not feel compelled to buy it if you at least like the idea behind the game. Doesn't help that the first impressions are exaggerated most of the times (either by the press or gamers).
As I grow older I also get much more money I can spend on gaming. When I was a kid I would only get maybe 4 games a year, as a present on big occasions. Now that I have the possibility, it's inevitable that I tend to buy more than I should (specially as money increases and my free time decreases). With this also comes the opportunity to "vote with my wallet". Sometimes I'll buy a game at launch or on a sale, even if I'm currently playing another game, just to support the devs.
Other thing, gaming sales are now much better than ever! Every 2 weeks you can get a good game with a good discount, and that makes it really hard not to bite.