Why would you assume people would no longer own cars? Wouldn't the more logical progression be that people buy Apple (or other self driving cars) to replace their existing cars? Otherwise you would need to schedule a car every time you wanted to leave the house?
No, because Apple doesn’t make inexpensive anything. Electric cars with self driving features are already expensive and out of reach of the mass market. Add the expected Apple tax and you’ll quickly come to the conclusion that Apple isn’t building a car to sell to the mass market but instead building a service that keeps them competitive with the likes of Google and Amazon who are absolutely going to do the same.
Apple didn’t start a TV streaming service because they thought they’d make a ton of money selling tv subscriptions. They did it to protect their position. Netflix was already using its heft to push Apple around and say “No!” to UI consistency and tvOS standards. Apple couldn’t afford to be pushed around by tv streaming services to the point that they’d compromise their user experience. So they became one themselves.
The same will be true of cars. Apple is building mobility as a service and an experience in Apple’s vision so that they dont get pushed out when Google inevitably does the same.
In closing, one just needs to look to recent generations to know that cars aren’t valued as they were when we were kids. Out of the dozen plus driving age kids in my family, only one has a license, none have a car that they drive regularly. Heck, I love driving and I haven’t owned a car in years because Uber has made it so convenient to just hop in a conveniently hailed car and get someone to drive me somewhere and not have to find parking or worry about insurance and maintenance and all those things. If I got a car now, it would be a classic that I take out every so often for the pleasure of driving, not for every day mobility.