Because not all cars in America are American cars, nor are all players Americans, regardless of where the game is set. It would if it comes with the restriction that the cars have to be legally available and common in Australia. A game full of Falcons, Commodores would be fun for a couple of hours, but it'd get old real fast. There's far too many good sports cars that we simply cannot get over here. Also, Australia has some good driving roads but 95% of it is drive straight for 30 minutes, small kink, continue driving straight. It's a solid ten hours between major cities. There's no real mountains to speak of in the entire country, so that's out. Plenty of lovely winding roads through bush, and some stunning coast roads, but the believable variety of scenery is much lower than that afforded by something like Southern Europe. If you wanted to set a driving game down south, you'd do it in New Zealand. Great scenery and the whole country is made up of windy B roads.