Well I certainly hope you aren't thinking about getting a new car while you're driving, but that's not my point. The point is that in a game you're trying to complete the objectives to get to a new car. Yes it rewards you with money to buy a car, but you're trying to get a car nonetheless. As far as I know, PGR2, Flatout, and Need For Speed series have cars locked and as you go through the game you unlock (or you buy) a new car and to finish teh game 100% you have to unlock (or buy) all the cars. Even GTA has a system like that. Sure there's cars roaming, but there are a few specialy cars that you can't get unless you cheat (which is dirty and no fun) or complete the mission.