We make special lanes for cars with multiple passengers b/c we think driving alone contributes to congestion, emissions etc. Driving with 0 passengers might be best for the companies, but for the same reasons, is not in the public interest. I think it's entirely appropriate for the public to place stringent restrictions on rides which do not move people or goods usefully. If you need high utilization, figure out deliveries and freight. Do _something _ useful.

It might be cool if someone developed a human-like robot that walked and talked independently ... But not cool if that robot walks in crowded places, doing nothing in particular, and stopping inexplicably. I would expect it to be shoved down a stairwell on day one. It just turns out cars are a little more challenging to shove.