Humans get into accidents all the time. Is that not unacceptable for you?
I feel like people apply standards to self driving cars that they don't to human driven ones. It's unreasonable to expect a self driving system never to fail. It's unreasonable to imagine you can just let it practice in simulation untill it's perfect. This is what happens when you just narrowly focus on one aspect of self driving cars (individual accidents) - you miss the big picture.