I don't follow why AI vehicles need to be 100% good. Plain old human-driven vehicles sure aren't and we accept their utility as being worth the trade.
Even if AI cars are statistically better than humans on average, it's an issue of control. It's true that most accidents are avoidable and caused by human error, but most people are (perhaps overly) confident in their own ability to drive safely (this is also why people text and drive).