When I made a special assault rifle for my Lone Wanderer Cho (who lives in The Citadel) I did boost its Durability (whatever that stat is called).
Because I figured here we have THE Citadel, which I assume has some sort of access to better materials, better scematics, whatever. Maybe they've retrieved FBI archives and other classified documents, whatever. So in that case, I did make his gun last longer. I also added a respawning "Gun Cabinet" which adds a new Citadel Assault Rifle every 3 days. I figure those Scribes or whomever are constantly working to improve my character's Lone Wanderer experience, since he IS the only one who actually goes above and beyond in most cases.
But for the average weapons we find in the Wasteland, those are all mutts. They're piecing crap together with crap.
I know nothing about guns, but as Clavier says, they do need frequent maintenance. That's the angle I like preserving, even if degradation speed is a bit untruthful.