I think this is really about the decline of miles driven in cars, not the decline in cars made or owned (although that connection surely exists). I live in a suburb and have a car, because having a house almost requires a car; hauling paint and wood and plants and things doesn't really work in public transport. That said I commute by public transport simply because it is faster (bus lanes and subway instead of traffic jams) and parking in the city would be over $100/day. So I'll likely never get rid of the car as long as I have a house, but commuting with it is just not an option.