Why do people find it so hard to believe that there's brigands in the Wasteland?
And who's to say they do not hunt, or scavenge when raiding isn't feasible?
Because in Fallout, they are clearly defined as "raiders", and raiding is what they've done since 200 years, on the same spot. A spot which would have been emptied of every single resource in less than a generation, for obvious reasons. A spot away from every single trade route, so there's not even incoming resources to harass. There's not a single production unit anywhere (mine, working factory etc.) to prey upon. Unlike vipers, they don't have a religious or demographic reason to raid or kidnap people. So what are they "raiding"? Ghosts?
Why keep raiding when nothing is stopping you from creating your very own kingdom? And if they turned to hunting, why would they keep raiding anything?
210 years is a VERY long time. 210 years ago, Napoléon had his claws on Europe. Germany did not exist yet. Slavery was still a thing. The U.S. were a very recent power, only held the east coast and was governed by the founding fathers. The secession war had not happened yet. We hadn't invented the light bulb yet, nor the trains, nor the radio, nor photography, nor the Vaccine. The Eiffel tower wouldn't appear before many decades, almost nobody in France spoke French yet... Between then and now, we are about to see the secession war, the end of the Napoleonic wars, the fall of the eastern Empires, three major wars, the birth of the U.N. etc. Since 210 years, we passed through a LOT of artistic genres, invented new musics, new paintings, discovered photography, the cinema, the radio etc. If we came to meet someone from 210 years ago, we would have NOTHING in common and we wouldn't even recognize anything from our respective timelines.
What I'm saying is, 210 years is enough to completely change EVERY single thing in every civilization.
Compare that to the commonwealth. What difference between the commonwealth, let's say 40 years after the bombs and the Commonwealth we see in Fallout 4?
Nothing.
In 210 years, the commonwealth citizen haven't built anything. They haven't moved anywhere. No political power emerged anywhere. No town has been built. Not a single government was born. Nothing was repaired or discovered. No resource has been produced. No new art and culture was achieved. Nobody repaired Sanctuary, or Boston, or Concord. Yet, everything stands still, every tree, every building, everything has been standing still for 210 years without human intervention, without the animals taking over.
I'm okay with that, if there's a reason. Thing is, there is no reason given why nothing changed, including raiders.
The only explanation is that the commonwealth is trapped in a time loop, basically a Groundhog Day extended to a whole country, and it has been as such since a century. That would explain why raiders are still raiding instead of being an actual civilization, again and again, forced to respawn and raid the same place at the same time, over and over again, for eternity.
Brigands are not raiders. Brigands make sense : outcasts, criminals and deserters sticking together and attacking supply routes for their own gain or to cripple a specific political force. And brigands always have a place to defend. In that sense, Skyrim's brigands make perfect sense. There are different political forces moving around, including military ones, there are trade routes and abandonned forts that have been taken from them.
To have outcasts, you need a civilization that rejected them. You cannot be an outcast of nothing.
To have criminals, you need to have a law system that defined them as such, and law enforcers that put enough pressure for the escaped criminals to hide.
To have deserters, you need to have, at least two military forces around the place of action.
To have raiders, you need to have supply routes.
To have VERY long term sustaining raiders (aka, one generation at most before their children leave them for better living conditions at a city, unless they form a tribe) you need to have a place that can protect them, like forts, supplied military bases etc. Gunners "could" make sense in that regard, but they are the exception.