This is true for me if I’m going to the park or camping or something like that, but for a typical day at the office or shopping, I don’t really need to be carrying around a carload of stuff.
There are many small conveniences that come from having a personally owned vehicle, but I would ecstatically spend an hour or two loading/unloading my car every couple weeks when I go on a trip as long as it meant I didn’t have to sit in traffic for hours every morning because everyone wants to have their own personal aircraft carrier sitting outside their office for whatever reason.
Thats exactly the struggle I choose to grapple with as a carless city person. 99% of my day-to-day, my bicycle and/or my backpack and feet are all I need and I love it.
But the car industry at large is so invested in this car-as-sanctuary idea that jumping into a random rental is often a frustrating experience. Pairing a phone for navigation or audio is a whole big thing. Finding a place that can rent a companion bike rack or other accessory like that for an outdoor trip is difficult, and supplying your own is usually forbidden - if you even feel comfortable betting on a generic enough model. Those 1% of activities where I really benefit from a car can be really difficult without the aid of a friend who owns their own personal vehicle, and it feels like that is by design a lot of the time.
My hope is that the proliferation of “transportation as a service” will eventually get to the point where all of those frictions you mentioned will be alleviated. If we stop treating cars like a personal sanctuary like you mentioned, perhaps we will get more focus on things like painlessly connecting your phone to a new vehicle at the tap of a button or making bike racks more commonplace.
One really difficult problem to solve is child car seats. That’s definitely no item you want to take to the museum and then just install in the next car for the drive home. My family did a few city trips where we wanted to use Uber to get around and it was a very frustrating experience.
I'm not sure it's by "design" so much as catering to very specialized tastes is difficult/expensive. Add to that, the sort of people wanting "outdoor trip" vehicles are probably going to stress those vehicles a lot more than the person renting a car to drive 30 miles from the airport and back.
There's a reason renting Jeeps in Death Valley is something like $200/day--assuming you have your own insurance that will actually cover how you intend to use it.
There are many small conveniences that come from having a personally owned vehicle, but I would ecstatically spend an hour or two loading/unloading my car every couple weeks when I go on a trip as long as it meant I didn’t have to sit in traffic for hours every morning because everyone wants to have their own personal aircraft carrier sitting outside their office for whatever reason.