I think the implication was that having any human drivers on the roads negates a lot of the potential benefits and safety provided by robotic cars. The drivers don't have to be bad to be worse than a robot. Driving a car yourself might go the way of riding a horse for transportation. You can still do it, and have lots of fun, just not down most city streets! Robocars would still have accidents, but hopefully more on the frequency of planes :)