Time is the answer. Very rarely, covering typical US population density to the routes and schedules allow people to get from point a to b in a reasonable time. I once tried to hire a person to work for our company who thought she could take the bus. To get three miles, it would take her roughly 3 hours and require her to change busses five times. In the end, spending six hours on a bus or waiting for one just wasn't worth it to work eight hours.