You've been able to see this coming for some time now, and it seems like the barriers continue to fall as we now have a licensed insurance broker who will provide trip-based insurance benefits and coverage for the passengers which include lost property, trip interruption benefits and even medical expense reimbursement. You can turn protection 'on' for individual items they own and simply pay for the protection you need. I suspect this may be much like declaring the value of your package when shipping it through the mail. We should be able to see this roll out more in the Phoenix valley in 2018, which happens to be where I live. I see these cars rolling around all the time, I even signed up to be a passenger but never got any further communication.
https://www.prnewswire.com/news-releases/trov-and-waymo-partner-to-launch-insurance-for-ride-hailing-300573229.html
https://www.prnewswire.com/news-releases/trov-and-waymo-partner-to-launch-insurance-for-ride-hailing-300573229.html