Even in major cities in the US, the vast majority of people still drive most places. Sure, downtown office workers can usually walk to get lunch, but that's about the extent of it. Also, exercise is much harder in urban areas, cities have crowded gyms making it harder to work out at peak times, crowded roads making it harder to bike, and constant crosswalks making it hard to get in a consistently-paced run. Rural/suburban people just run on their land/around their neighborhood.