I dunno, but my reason depends on the actual game. For example something innocent like lets say NSMBW. I play it for just the entertainment (and nostalgia). Other games that are ultra violent such as Modern Warfare 2 or Grand Theft Auto, is mainly as a stress reliever. If I ever feel like I want to just bring a knife and stab someone or something (using that as an example, I never feel like doing that) I can just switch on GTA and start massacring people without any consenquences on my part (yes I use cheats on that game

). Plus it has been proven in studies by psychiatrists that some video games that involves the use of basic motor skills such as Guitar Hero, is actually great as it does just that, helps patients recover the use of basic motor skills. Plus like I said, its also been proven that games like GTA is a great way to relieve stress.