There are a host of obvious reasons why even a "simple" human will beat an L4 car hands-down:

* Lack of software bugs due to careless programming.

* Millions of years of brain evolution allows adapting to unforeseen circumstances.

* Vastly decreased likelihood of being tricked by vandals exploiting flaws in recognition algorithms.

* Inability to be hacked en masse and driven into each other/houses/pedestrians.

* Much harder to back-door.

* Can be judged in court if they swerve to avoid a pigeon and hit a crowd of pedestrians.

I could go on, but this should drive the point home pretty clearly, IMHO.