It's a pilot program for legalizing on road research projects. Presumably, someone felt that two people paying attention to the autonomous actions was better than one.

One paying attention to the research and one paying attention to the traffic situation sounds like the right division of labor.

In my experience you need the driver to fully pay attention to the road with one hand on the kill switch and the other on the wheel while the passenger works the computers doing the driving. This is just legislating common sense.

These are Research Vehicles, not final products.