Another huge problem is that error rate it not error shape. We have an enormous body of knowledge and process for guessing what might cause problems for human drivers, how to deter the problems, and how to mitigate the damage.

For example, you'll have a pretty good idea how our fellow humans will react to rumble-strips if I describe them or play a recording. I don't need to consult a datasheet or design an AI test suite with a zillion simulations and a bunch of closed-course tests.