Boats and aircraft are both different from automobiles. They have full freedom of movement. You can't set a course in the same way with an automobile, because the automobile will need to follow a roadway and possibly make turns at intersections. Boats and aircraft can have waypoints, but those waypoints can be mostly arbitrary, whereas a car needs to conform its path to the roadway, traffic, signage, etc.

It's an entirely different domain.

Yes, an autopilot is not what you need on a car.