… because … Freedom!
Realistically, an actual ban on cars is not going to happen, but seriously, we do need to look at the issues and impacts related to pervasive car use.
There are the obvious concerns about safety, pollution and profligacy, these can be addressed more effectively by someone else because, as far as safety goes, I believe cars have become too safe – I would favor banning seatbelts, airbags and windshields just to make driving a less desirable option.
One major issue related to cars that always gets overlooked is their de-socializing effect. We get into little closed cages that separate us from everything around us, and driving becomes a martial art where everyone else is the enemy, an impediment to our rightful progress or a potential collision. And between where we are and where we want to be, there is this sort of cinematic interlude going by. This is in fact related to the gun issue inasmuch as we have become a macro-cube-city where interacting with others tends toward being a hostile act.
And because everyone is acquainted with this behavior pattern, the roads have become the sole property of the car. People fear riding a bicycle on the road because cars are large, stupid, painful and the airbags are for some strange reason on the inside. So alternative ways of getting there are gradually consumed by the automobile. Practical public transit does not exist (except in cities) not because it is inefficient (quite the opposite) but because fuel is terrifically underpriced.
So there is your first answer to addressing the problem with cars. You cannot ban them, but you can make them nearly beyond practical reach by raising gas taxes. The revenue from the tripling of gas prices would go in part to improving the alternative transportation infrastructure: more buses and real enforcement of crimes against bicycles and pedestrians.
If we can get out of our cars, we would almost certainly be a healthier people, actually using our muscles to walk or ride places (I could realistically walk two miles to the grocery store, but the car traffic makes that walk rather unpleasant) and more likely to feel like we are moving in the world instead of through it AFAP.
Oh, and one other thing: there was the guy who abducted an 8 y/o girl from a playground by shoving her into the back of his car. Not having a car to do that with sure would have made it a whole lot more difficult for him to do that.