That's fine when a few people want a car in the city, but when millions of people in a busy city want the same thing, then it's unsustainable, there's literally not enough room for everyone to have a car since (even ignoring the amount of road space you need for everyone to drive around after they get off the high-speed car-train) you need two spaces for every person (one at home, one at work) -- the size of a person's required parking spaces (and the travel lanes to get to them) approach the size of an urban housing unit, so parking alone cuts urban density by 1/2.

The kind of low to mid-density area that can support everyone owning a car is not the kind of high-density area that can afford to pay billions of dollars for high-speed car tunnels.

If you want to use your car, use it outside of the city, don't displace housing in the city so you can park your car for the 22 hour a day you're not using it.

I may find it very convenient to drive every where in my 40 foot motorhome so literally all of my stuff is with me at all times, but that's not going to happen.