It's commonly brought up saying, and I don't think it's too far from the truth.

Driving under every condition requires a very deep level of understanding of the word. Sure, you can get to like 60% by a simple robot vacuum logic, and to like 90% with what e.g. Waymo does. But the remaining 10% is crazy complex.

What about a plastic bag floating around on a highway? The car can see it, but is it an obstacle to avoid? Should it slam the brakes? And there are a bunch of other extreme examples (what about a hilly road on a Greek island where people just honk to notify the other side that they are coming, without seeing them?)