Right now, there would be some resistance, but I think you underestimate just how much people are to used to subscribing to services. This includes hardware and software. If I lived in the city, it would be a no brainer for me. No searching for places to park (and pay). No worrying if someone breaks in to my car or vandalizes it. No having to take it to the shop for tune-ups and inspections and all that for cheaper than what it was costing me to own a car. If a car's purpose is getting me from A to B, it is still the most direct option in most cities. Take Asheville for example (I live here and know the area). There's a bus system. The trolley is for tourists. But that bus system will not be efficient for the individual both in time and energy, if that individual lives half a mile or more from a bus stop. The city cannot afford to add more and more bus stops to ensure everyone's home is near one. The roads are already in place, and would have to be maintained for the buses (and other services that use the road such as emergency, police, fire, mail, etc) no matter whether or no subscription car services exist. With cities that are VERY huge, mass transit already forces people to have to abide by a bus schedule as well as a work schedule. People want freedom of movement.

I'm very pro mass-transit. But it cannot be held up as the singular fast transportation solution for a society. The subscription service is not meant to replace mass-transit. It is meant to reduce noise, emissions and traffic at the benefit of more affordable transportation for those who cannot always use mass transit. For example, I might have a subscription that gives me a certain number of miles per month. Now normally, I take the mass transit to work, day in and day out, but maybe on the weekends I like to have a night on the town with my friends. The car comes and gets me, drops me off at the club right where my friends are. We drink, we have fun, bouncing from club to club. End of the night, I push the "come get me" button on my app and the car will pick me up and take me to my house. I can use mass transit, but also have reason to want a quicker option than waiting on the bus schedule. Nobody obsesses over what someone is driving. We're all just ferried around by the service.

And we have seen how fast populations will adopt something if you hit the right buttons.