[topkai22]

Also there are a fair number of smaller cities that have physical obstacles (mountains, bodies of water) between them and a major airport. I used to fly with a connection between Chicago and Grand Rapids, MI regularly. That's a 50 minute, 220km flight, or a 3 hour 315 km drive (assuming no traffic). Plus, embarking/disembarking at a smaller airport lowers total time as well.

I actually think you the cargo aspect will be somewhat significant as well- The regional airports I checkout on flightaware appear to have several fedex/UPS feeder flights a day.