Flying cars haven't caught on because they're a solution looking for a problem.

Take every cost, every annoying thing, and every risky/dangerous thing about driving and multiply it by 100.

Even with a magic UFO gravity motor that just lets you float around on a tiny amount of energy and with perfect safety, pretty much all the problems still exist if there are a substantial fraction of people using them. The traffic control alone is a nightmare because now it's in 3 dimensions and higher velocities.