People in the US typically only take domestic flights between major cities and usually only if they are traveling a long distance (across multiple states).

One reason for this is because you usually have to rent a car when you reach your destination anyway. So if you fly two states away to visit family, land in the closest city to where they live, now you have to rent a car at the airport and drive a couple of hours to their house. You've now paid for a flight and a car rental and you probably could have gotten there cheaper and just as quickly, if not faster, if you drove.