There is a big difference between a plane (or a boat, where autopilot is also common) and a car. A plane or a boat is roaming in a vast, mostly empty space, in

There is a big difference between a plane (or a boat, where autopilot is also common) and a car. A plane or a boat is roaming in a vast, mostly empty space, in a straight line. Other planes/boats are both pretty far away and also following a mostly straight line. On the other hand a car operates in a very packed space, full of obstacles all moving in sometimes unpredictible way. That makes a huge difference when it comes to autopilot.