I've been to a couple lesser developed countries over the years and it was quite obvious to me that in these places a tremendous barrier to economic mobility was the lack of any kind of decent transit system. They primarily urbanized during the age of the automobile, and what infrastructure money they had was spent on "modern" roads. But in places where wages are such that "average" people can't possibly manage to purchase and maintain an automobile, those people are pretty out of luck. And automobile-centric development makes things worse, spreading things out and making decent transit more difficult and expensive to implement.
Increasingly, it's a problem here too. Arguably the problem isn't sprawl, but low wages, but given the low wages the sprawl is a problem.
