I think they got it backwards. It's suburbia that let's you use your car door to door.
I haven't done the study, but based on my observations walking is one of the favorite activities of inhabitants of my city. In fact people come from far away just to spend the day walking around. Some is leisure, but one can't help but to introspect when left on pavement for too long.
another person known for his walking was Arthur Schopenhauer. He walked for 2 hours every day regardless of weather conditions[0]. I read about this long time ago and it left a lasting impression.
but walking is not the only activity that is good for introspection. For me driving worked just as well. I miss driving.
[0]http://www.apieceofmonologue.com/2009/06/day-in-life-of-arth...