Well, the easy answer to the guns question is simply... "Murica." I posit the people most likely to survive the war depicted in Fallout... if you are looking for realism and a "coherent world," are the kind of people who would undoubtedly prioritize guns over houses and the skeleton cleaning out thereof.
Again, the war depicted in which Fallout?
Because again, in Bethesda Fallout the nuclear war happened, the survivors all grabbed guns and ran around shooting each other and drinking from the toilets for 200 years. Presumably, new ammo just popped into existence to replace the ammo that was expended, and new humans grew out of the earth from dragons teeth so that the survivors would always have someone to shoot and loot. Also, despite guns in game breaking permanently after firing a few hundred rounds max, the supply of guns was so infinite that people never ran out of guns and just kept finding more guns all the time.
In West Coast Fallout, there are entire societies which either don't use guns at all, or where guns have a special status. Ceasar's Legion controls the entire state of Arizona and a big chunk of Colorado by the time of New Vegas, but most legionaries are using spears or machetes. It's not because they hate guns and threw all the guns in the bin, the elite soldiers of the legion often do use guns, it's because Arizona was mostly inhabited by tribal societies who for the most part had abandoned guns in favour of more sustainable weapons, because there wasn't a complex enough social organization that people could afford to spend their lives making powder and ammunition, refurbishing and repairing old guns or making new guns.
Again, the west coast nuclear apocalypse is stadial. Things change. People didn't just run around shooting each other for 200 years because they would have run out of people. Society declined and rose in response to changing circumstances. Guns became viable again because people started forming communities which could support them, but a lot of people stuck with spears and it makes sense that they did, beyond being an aesthetic reference to the post apocalyptic genre.
But most people screaming about how awful Bethesda was to the property, positively gush about how New Vegas was the "true sequel" and was "more faithful" to the originals. So, how rare were guns in FO: NV? Not very rare.
You know there's an actual literal working gun factory in Fallout: New Vegas? One of the missions is to break into it.
Again, in the West coast setting it is is generally explained why there are so many guns. People make guns. There are industries devoted to making new guns and refurbishing and trading old guns. There are groups and gangs, like the gun runners, the van graffs and the shi, whose entire role in the economy is to make, fix and sell guns for profit. People are not just finding an infinite supply of random ancient guns.
But, for me its a good thing I'm not looking for a coherent world. I'm looking for a fun game.
Me too.
But it doesn't sound like you're looking for an immersive roleplaying game. It sounds like you're looking for a shooter with post apocalyptic aesthetics, and you're in luck. There are a lot of those. Sadly, there are considerably less post apocalyptic immersive roleplaying games.
I'd put my money on the few survivors after the war all succumbing to suicide, the guns of the other few survivors, radiation, disease, and the final few getting picked off by mutated flora and fauna. I think simply being able to look past the almost certainty I have that there would be no survivors, kind of immunizes me against the handfull of other valid/notvalid so called "plot holes" in any of the Fallout games... Bethesda or not. Because in the "real world" we'd all be rotting, either above or below, the irradiated earth.
Honestly, that sounds like your hangup more than anything else. To me, the idea that all humans would simply kill themselves if the internet went down or mindlessly fight each other to extinction isn't realistically depressing, it's just trite anti-humanism.
The great thing is, there's a game which deals with these themes very directly. You might have heard of it, it's called
Fallout: A Post Nuclear Role Playing Game.
Fallout is about a human survivor travelling a world where humanity is still on the brink of annihilation, and ultimately coming up against an army of mutants lead by a being who has given up on humanity and decided they're too weak and doomed to tear themselves apart in a cycle of endless violence, and who believes that their solution, terrible as it is, is the best hope for what is left of humanity. For a game that is so dumb and edgy and hilariously dated, it still evokes emotions in me decades after I first played it, and that's ultimately why I still care about Fallout. It's not because the combat was really good and you could make people's heads explode, it's because the writing forced my tiny child self to consider what I thought, what I believed and where I stood in this conflict between hope and despair in a way that I still remember and like to think about, and that to me is as much the sign of a good game as being able to pew pew the bad men until they fall down.
