> probably cheaper than the status quo, but less convenient
If it lets you get rid of your cars, maybe.
If you also need a daily car (or even two), rental is not necessarily cheap, and beyond convenience it has flexibility issues.
For instance the rental closest to me is a half hour bus ride away, and not open on the weekends, and the prices can vary a lot depending on time to trip or period, and obviously the type of car can triple the rental price.
It’s worth it to me, because I can otherwise get by fine without owning a car. But if I need a daily anyway, it makes more sense to upscale it a bit and get the extra freedom. Especially if relatives start getting up in age and you never know when you need to pack up quick.
It’s the same issue with timeshare vehicles, if people have kids they’ll all need it at the same time (because school schedules), and you’ll always remember when it was not available for an emergency.