The reason Forza and other racers with real world cars were able to put damage into their games is because of the success of GT. When GT was first being made and they wanted all these real world cars in there, car companies didn't want their cars to be shown in a negative light (as in breaking down in a game). With GT's success, other developers were able to leverage damage into the game while Sony was probably stuck under a contract to not allow it in.
As for why it isn't in the prologue, probably because they are selling it online and want to reduce the size of the game. think about it, 75 cars with damage code would greatly increase the size of the file, and to make sure damage works right since it would be the first time that the devs have put it in the game.










