A self-driving car AI pays less attention than a human driver at his best. It isn't as aware as a human driver at his best. It doesn't have the spatial reasoning, the intuitive understanding of physics and road dynamics that matches that of a human driver at his best.
Human drivers still fall behind statistically, because human drivers are rarely at their best. And the worst of human drivers? It's really, really bad.
AI is flawed, but a car autopilot doesn't get behind the wheel after 3 beers and a pill of benadryl. It doesn't get tired, doesn't get impaired, doesn't lose sleep or succumb to road rage. It always performs the same.
Until it gets a software update, that is. The road performance of an average car AI only ever goes up. I don't think that's true for human drivers, frankly.