@LogicalApex I totally agree there are secondary benefits to keeping these cars on the roads such as collecting data, moving cars to destinations where there might be pick ups in the future, and arguably even free advertising, but my friends in the industry say that the main purpose of deadheading is to save money.
@docpop I am sure that plays a major role in it. Does SF have parking metering infrastructure that would allow the car to accurately pay for street parking?
I could also see people getting fairly upset if you have a lot of self-driving cars parked in a busy area making parking harder for cars driven by people.
I'd expect Waymo and others to use private lots to sidestep those issues when they need to park.