Vehicles today are subject to hacking and thus remote control by a third party. Now take a bunch of these self drivers in heavy traffic with some really good hackers and you have a real nightmare.
Imagine other great opportunities. Bomb delivery by terrorists. Kidnapping. Murder by driving into a lake/river with doors permanently locked. Drug trafficking to avoid getting caught.
All this sure makes that 1995 Silverado look good.
If self-driving cars end up being all that is available, I will be switching to a good fence jumping Missouri Mule.