Differences.

While airplanes come in all shapes and sizes they have a number of differences from the flying car concept. They require dedicated areas to operate. Can't just set one down in front of the house or like that. Pilots receive specialist training that goes well beyond your average road exam. And since airplanes don't suffer from the design constraints of the concept of flying cars (think objects the size--at worst, slightly larger--of the average automobile), certain aerodynamic considerations can be factored in to make certain kinds of failure a less-than-catastrophic affair.