This is rarely mentioned, but… you get a SDC. It starts driving you around. Until it runs into something it can’t handle, and hands the wheel back over to you. But you don’t actually practice driving anymore. And you were playing games on your iPhone.
Because SDC, amirite?
No one can context-switch like that in the space of reaction times measured in fractions of a second. It defeats one of the reasons for SDCs if the pilot has to monitor it all the time.
Planes get away with it because largely there’s nothing to run into up there, and also co-pilot. Unless you’re in the Blue Angels (or a glider pilot on tow), you’re not flying close formation as a United pilot. Gaps are measured in minutes and 10ks of feet.
And skills require practice. This is a thing with planes too, that has to be addressed in training – more things are automated, so pilots get less real-time practice. Accidents are attributed to this. And airlines require simulator time on real simulators, not GTA on XBox.
There’s no intermediate step where we have part-time self-driving cars with a human monitor to step in. It’s all or nothing.