I thought I had used my MTB to live my "general purpose" daily life in a very hilly area for a few years now, guess I was wrong cause that's not in your list of preapproved uses.

I would think that having a vehicle that's completely silent, easily stashed, easily maintained, faster than any zombie on any terrain except maybe up cliffs, that can easily haul 50 kg of bullshit on the rear pannier would be useful. But apparently I need something more general purpose? Like a car I can't maintain long-term that becomes fully immobile if an important part breaks and can't clear even the most basic of obstacles?

A motorcycle makes a lot of sense as well but it's very noisy, less adaptable to rough terrain, tougher to maintain, and still requires a continuous supply of gasoline which will go bad in a few years anyway. I'd probably still have one but not for daily errands because that would just be a waste.

I really hope your dystopic scenario has dedicated crews or movie magic to clear out the highways of fallen trees, rockfalls, and bramble patches because I don't know what you plan to do about those on a 4-wheeler after a couple years. I think you are vastly underestimating the civilizational work it takes to keep motor vehicles a viable form of cross-country transport.