You may disagree with the reasons for your own reason to not finish something, but they are the most common reasons. Personally a finish a lot of what I play, sometimes multiple times, but the one genre I always struggle with is open world. I've only beaten GTA3, never finishing RDR or GTA4 (or any of the GTA3 side sequels). Nor have I had the drive to finish New Vegas, though that is in part due to how much FO3 I played. (read: A LOT) The main thing that stops me from finishing a game is either annoyance or boredom. If some aspect of the game irritates me, or the game just doesn't pull me in the way I believe it should, I won't finish it. And likely will never even return to it. Even games I like, like Super Meat Boy. It's a good game, but sometimes it's too vindictive for me to care. I will never be one of the insane people that can get Impossible Boy or anything, so can't be bothered.