3. Restricted airspace. They’d never fly in the immediate DC area, for example - it’s mostly a no-go zone with exceptions for National Airport and College Park Airports. The restricted zone actually extends beyond the beltway - which excludes the space where traffic is worst and flying cars would be most useful. (Freeway airport in Bowie has a section of the restricted zone carved out for it, but the airport is closing.) Even if you are authorized to fly into the zone, it’s not as simple as, “Hey today I need to drive to Georgetown.”

DC might be an extreme example, but I assume many cities have restrictions on flights above them.