Cars are different than a lot of goods though, because in and of themselves they are a wealth signal (at least in the US).
Most Americans don't really need an SUV or a pickup; a minivan or a sedan are more practical. Yet most Americans are buying them, because it makes them feel better about what they're driving and they want to show off. You may only take your car to the grocery store, but if you meet Becky from PTA in the parking lot and she has a really nice car that she owns, that's still a big deal.
Unless the ownership cost of a car were to spike significantly, this part of American culture seems hard to change, particularly when automakers spend lots of money making sure that Americans see premium gas-guzzlers as status symbols.
