> Ever consider if the effective duty cycle of your car is increased the vehicle wears out quicker?
Sure, but by how much? What's the average extra overhead per person? By that I mean, what's the average distance that a taxi would need to drive between dropping one person off, and picking the next person up.
The more taxis there are, the lower the overhead, as the more likely it is a taxi will happen be nearby to someone who wants one. We're used to taxis being rare, especially outside of major cities, but if taxis were common, the overhead might be very low.
I can look outside right now, and see maybe 20 vehicles parked within 50m of my home. If that were 5 self-driving taxis instead, that would be easily be enough capacity for my immediate neighborhood, at least most of the time.
So you could likely reduce the amount of cars locally by a factor of 4 or 5, and I'd still have a vehicle less than a minute away at most locations. Yes, if you had a 5th of the cars they'd have to do 5 times the work; but likely not much more than that. In other words, the maintenance cost wouldn't significantly worsen, and may even improve; cars aren't immune to entropy while stationary.
The other advantage of having self-driving taxis is that you can more easily specialize. I have a pretty typical 5 seater car because I sometimes need that space. But most of the time, I could make do with a 2 seater with half the mass. My choice of car is determined by the edge cases, but my choice of taxi would be determined by what I needed at the time.