I feel like a car has greater potential for comfort than even a "comfortable" reclining bus seat.
For example, right now the idea of a folding bed in a car isn't something you'll ever see as an option, since it would only really appeal to people trying to live in their cars, which probably don't overlap much with the "people who buy fancy cars with fancy extras" market segment. However, in a future where a car can auto-drive you on a long-distance trip, why not offer an actual bed mode in the car as a purchasable option?
Improbable, unless you can handwave terrain away. (And deer. And malfunctions. And...) There's so many things a car can impact besides other cars that a non-seatbelt in a car is far less likely than cars being replaced by some other form of transport.
For example, right now the idea of a folding bed in a car isn't something you'll ever see as an option, since it would only really appeal to people trying to live in their cars, which probably don't overlap much with the "people who buy fancy cars with fancy extras" market segment. However, in a future where a car can auto-drive you on a long-distance trip, why not offer an actual bed mode in the car as a purchasable option?