Technology

Not really. Many planes can get about 20 miles per gallon traveling at about 180 miles per hour. That's slightly more than a family car, but not astronomically more.

The big differences are that there's effectively no "traffic" in the air, so once you dial in a cruise speed you stay at that speed for the entire flight. In a car you can get stuck in stop-and-go traffic. There's also the lack of "rolling resistance" in the air. Even if you're going a steady speed on a highway your tires are a source of drag. On the other hand, taxing and taking off can burn gallons of fuel, so unless you're going for a fairly long flight that's a significant part of the fuel burn. Also, planes go in a straight line, whereas cars have to follow highways. But, the total fuel cost of the trip really includes the trip to/from the airports.

But, fundamentally, the fuel economy of cars and airplanes is pretty similar.

They're working on next generation air traffic control, that is automated and also can handle drones whizzing around next to flying cars, but developing that isn't fast or cheap or deploy and will need extra equipment on the ground and in the cockpit.

Also, imagine drunk flyers in bad weather.

I can't imagine an "open to the general public" flying car system that didn't involve huge amounts of automation, basically self-flying planes. A modern jet liner is effectively self-flying already. And, even though the pilots are rarely required to take direct control over the jets the alcohol limit is 0% and they're not even allowed to drink within 8 hours of a flight. So, to have a scenario with "drunk flyers in bad weather" you'd need a system with looser rules than current aviation, and less automation that current aviation.

Also, there’s no air bag in the world that can save you in a crash.

No, but there are parachutes.

Besides, most fiction involving flying cars also involves automated flying cars. Sure, often the "hero" takes direct control of the car and does some crazy maneuvers with it, but in the futures where flying cars exist, autopilots are extremely advanced, and most commuters just hit the button and relax. In addition, if an autopilot did exist, it could become "driver assist" if the human decides to take "direct control". So, even in a future with frustrated aerial commuters who get "sky rage" and decide to take over flying from the autopilot, a "pilot assist" program could still interpret what they want and limit the danger they pose to themselves or other craft.

The F-16 is almost 50 years old now, and for those 50 years it has been impossible for pilots to fly it with "assists off". The plane was designed from the start to be dynamically unstable. A pilot simply couldn't control it without computer assistance. The pilot uses a fly-by-wire system where their inputs are interpreted by computers that do the right thing while still maintaining stability and so-on. A future flying car would pretty obviously be designed the same way.