A 5x reduction in accident rate(plus the convenience of self-driving) , advertised and lobbied in the right way, can be translated to a huge political power. That could, with time, convince authorities, And that wasn't the case in the other systems you mention.
First, you do not need self driving car to achieve 5x improvement. Good driver assistance systems will get you there.
Then, put yourself in the choose of the politician that is authorizing this technology to be used massively. Picture the amount of cars that are going to run everywhere once this authorization is given and ask yourself: what will happen to him once the first hundred people have died because of a wrong autopilot decision (it will be such figures, since you are OK with x5 reduction). Do you think he will be sleeping well at night? Do you think his political career will be better, especially if you consider my first point? Would you step in his shoes?
