Because I am a fan of Escapism. Yes, yes I know I'm on the escpaist. But you know what I mean. I'm one of the few people who legitimately care MORE about the aesthetic (visual, spatial, audible) qualities of a game than it's gameplay.
I play Assassin's Creed, for example, because, not only will I never be able to actually BE a badass parkour-ing Renaissance Ninja, I'll never be able to glimpse the sheer beauty of Renaissance Venice period.
Similarly I won't be alive long enough to captain a sleek beautiful Warship to the farthest edges of our Galaxy with a kick-ass team of interplanetary warriors. And hence, because my life is infinitely more banal than ANY of those existences, I play Games.......
.....aaaaand that's the only honest answer you'll get OP ^_^