A helicopter can't go from flying to transport you in a highway. When people talk about flying cars they imagine that. Something that can fly and go around roads as a _car_ would normally do.
It's only when this was obviously impossible that futurists pushed the "mostly a car but can also fly sometimes" angle.
Yes and no. In some EU countries, helicopters accepted to land near highway, and pick up (or disembark) passengers just like ordinary taxi. Also there very typical case, helicopter landed near Gas station to refuel.
Generally, strict restrictions exists on flights over large cities, but over rural area and over big water, regulations easier. Even so, if in large city exists big river, aviation could flighting over it with very easy restrictions.
Flying cars are a fetish: because they are futuristic technology, therefore they are desirable. That is the motive force behind them.