There is a confluence of factors, I think: rigid zoning laws that prevent mixed-use neighbourhoods, the car-orientedness of recent construction (think cul-de-sa

There is a confluence of factors, I think: rigid zoning laws that prevent mixed-use neighbourhoods, the car-orientedness of recent construction (think cul-de-sac-neighbourhoods with one single outlet to a major highway), and of course the fact that once you have kids you are not supposed to have a social life any longer. American town planning has been a disaster since time immemorial.