Because I don't have it, but that's what happened to me last night when I finished Bioshock Infinite. (Even if I did have my suspicions about one of the multiple plot twists in the final moments, about three hours into the game.)

It's probably to early to start talking about Game of the Year stuff, but I'll tell you now, if this doesn't end up at the very top of my list... Well, this is going to be the best year for gaming ever, then.