I usually think about it in the other direction: every time an accident occurs, a human learns something novel (even if it be a newfound appreciation of their own mortality) that can't be directly transmitted to other humans. Our ability to take collective driving wisdom and dump it into the mind of every learner's-permit-holder is woefully inadequate.

In contrast, every time a flaw is discovered in a self-driving algorithm, the whole fleet of vehicles is one over-the-air update away from getting safer.