Actually, I think it's so difficult because self-driving cars is an engineering problem rather than a human one. It's like ironing and folding clothes. Looks really simple, but insanely difficult to build a computer to do it, because the domain is one that our brain is well-suited for, but computers are not. If we see a squirrel add numbers, we see intelligence; but we are not much impressed with a computer adding numbers. If we see a computer dashing among the treetops we see intelligence; but we are not much impressed with a squirrel dashing among the treetops. Self-driving cars are imitating human driving, and the imitation is hitting diminishing returns because computers are ill-adapted for the domain. We'd probably get more ROI changing the roads (the domain) at this point.You are judging this accident from such a human perspective rather than seeing it from an engineering problem.