The difference is that the aircraft autopilot system does not have to be that intelligent. My imagination is that if I engage an aircraft autopilot system I'm f

The difference is that the aircraft autopilot system does not have to be that intelligent. My imagination is that if I engage an aircraft autopilot system I'm free to do other stuff for >= 1minute, because it's enough to simply hold the direction and height. There are no sudden events. In a car however with the current state of automotive assisantance systems the timeframe for "doing other stuff" is less than 1 second because we have a fast varying environment there, including other cars (or pedestrians, bicycles, ...) taking sudden movements. Even many 5s situations can not be handled by todays assistance systems, like some surface conditions, traffic lights, track changes due to constructions, etc. Which in the end means you have to be constantly be in control of car, which is just not what "automatic" suggests.