No, nobody here knows why. We are not Polyphony Digital.
However, any car absent from the game is absent because of any one of the following reasons:
* They don't know about the car.
* They know about it, but don't want the car in the game.
* They want it in the game, but couldn't get a licence for it.
* They got a licence but couldn't get hold of one to model.
* They modelled one, but it wasn't in time for the game's release (or subsequent DLC).
Same goes for any other question of why any car isn't in any game.
