Package delivery subcontractors and couriers might also be out of business if a package delivery can be made on demand - when you are there to meet the car and open the trunk.
If car ownership plummets, and is replaced by on-demand services, businesses making/installing after-market accessories for cars would suffer e.g. stereos, parking sensors, etc.
AAA and other road-side services.
Towing companies would lose much of their business moving illegally parked cars.
For that matter, what if there isn't a manufacturer's shop in my town? I'm going to let my car drive itself to the next state and back, when it's already in need of repair? Um, no. You may have less local auto repair shops, but not none.
Same with rest stops. Over-the-road trucks won't need them, but the majority of highway traffic is cars. The people still need a restroom, even if they don't need a rest stop for fatigue reasons.