Mostly because he's assuming that an autonomous car will be exactly like a current car + driver
I won't assume anything, but I question how autonomous cars are going to negotiate with other cars, something I do on a daily basis. And I'm not just talking about the famous one-fingered salute. For example, to get out of my driveway I need to make a right hand turn on to a busy street that often has a long line of cars stopped at a light. I've found through trial and error that the quickest way to get moving is to roll my window down, stick my arm out the window, give the next car in line a jaunty wave, a toothsome grin, then I clearly mouth the words "Thank You!". Even if they previously had no intention of letting me in, since I've preemptively thanked them, 98% of the time they'll let me go (the other 2% are clearly sociopaths.)
Now with autonomous cars on the road how are such interactions going to be handled?