Probably because of people like me. I'm not a hardcore soccer guy by any means. I just want a game that plays good and looks good. I'm an unabashed graphics ho, I want my games to be pretty. Fifa is prettier than the other title. So as long as Fifa plays a decent enough game -- without any significant flaws -- I don't care if the other title is better game-play wise. I'll take the better-looking game with more licenses.
Oddly enough, I have the same view when it comes to women.