I think that the whole thing was designed as an intermediary step for the car sharing process, and was then adapted to prize cars so it had a use outside of multiplayer; at least that's my two cents on the subject.
Although if you're going to question car acquiring steps, what the heck is the point of the screen after you purchase a car? I have to see a loading screen, the car turns on, it drive forward like 30 feet, stops, the game pauses, THEN it asks me if i want to get into the car. Then ANOTHER loading screen back to the main menu. I really liked the way previous GTs (outside of GT5P) handled it, you bought it, they asked you if you wanted to get in it, end of story. They didn't have to make a freaking production out of it....uh..sorry about the rant there.
