250 miles isn't nearly as much as it sounds - you need to leave plenty of buffer in case something goes wrong so cut some of that off. You also need to get to an airport and then from the other airport to where you are going. Thus most of the time for distances of that range driving is faster.

The cases where I've seen this in use are from island to island (or mainland) - where a boat is much slower and there is no bridge for a car. A useful niche, but not general purpose getting around. There are also a few people who happen to live near (often on) an airport and work near an airport who will fly, but that is also a small niche.