Because it's FB. Pure and simple. Why would you think for one second that it would be anything different? You want to use/live in the FB environment, you play by their rules. That means using their SDK in all of your things deployed via their environment.
So in this case, it's good for the goose but not the gander when FB slaps terms on their platform, but not when Apple does it on theirs. Yes cart->horse, but you just know it's going that direction.
