To be fair, wet roads confuse human-driven cars, too.
The problem is that when they're wrong, they're wrong in ways that humans wouldn't be, and the wrongness appears to be "broken" to us and we overweigh these incorrect responses because they're both wrong and not human in their wrongness.
http://www.technologyreview.com/view/530561/the-revolutionar...
(discussed here: https://news.ycombinator.com/item?id=8290441)
http://googleresearch.blogspot.com/2014/11/a-picture-is-wort...
Especially in California.