Because deregulation has turned airline customers into the same class of folk who used to take the bus or train.
Because the TSA has so effed-up the boarding process that many people refuse to fly commercially.
Because by the time I get to the airport, check bags, submit to the grope, fly, retrieve bags, and rent a car, a trip less than 800 miles can be accomplished just as rapidly by driving, AND I CAN CHOOSE MY OWN FOOD! Furthermore, I’m probably not going to lose my luggage, be ripped off by a luggage “inspector”, nor will I need to change planes or have a layover.
Any questions?
Can I borrow your car? ;-)
Or maybe, I'll just avoid your airport.