I don't buy the idea that in a world where self-driving cars are safer, we should have 'less safe' human drivers just because we can blame them when they kill someone.

Car manufacturers shouldn't have to show something is perfectly safe, and IMO they should just have to show that something is reasonably safe (e.g. as safe or safer than a human driver in the same condition).

There isn't a requirement that someone has to take legal responsibility for every accident that happens in the world, just that people act with reasonable care and attention within the law.