1. Because facebook games don't cover all genres, mobile games do. Rpg's, racers, puzzle, adventure, action, fps. Everything is there. Also to play FB games you have to be online, and not many of them have mobile versions.
2. Steam is killing PC retail, I don't know why you think otherwise. More options is good sure, but handhelds are a dying breed I think. Or at least their significance will be reduced. As I said 3DS can still be big go kids and hardcore people, like you obviously.