I suspect one of them is some people get shockingly little exercise. When I lived in the suburbs, my daily could often be “walk to car, walk from lot to office desk (taking the elevator instead of stairs), walk from there to car (via elevator), walk from car to home”. Total walking time less than five minutes.
When I moved to New York I got at least twenty minutes of walking to and from the subway every day just going into work. Plus now I walk to the grocery and other stuff.