IDK why people act like Bethesda doesn't rebuild in their games, they are it's just slower
Capital Wasteland, two main cities, one of which, Megaton is a nightmare of issues ranging from water table to doing the reverse of defensive concepts (LIVE ON A HILL, NOT IN A HOLE!). The other is a damned aircraft carrier which somehow doesn't have any form of housing outside of itself, absolutely zero rebuilding over two hundred years.
Commonwealth has had two hundred years and to show for it we have 1 (one) major city which is inhabited by an entire clown-posse of retards ranging from people who misunderstand the basics of sports (there wasn't a SINGLE baseball game book IN A BASEBALL STADIUM?), to robots who only speak Japanese and sell noodles despite no farms being present.
Reminder that Fallout 1 takes place WAY before these two games and features...
-An entire functioning village comprised of Vault 15 descendants
-A big scrapyard town with functioning law enforcement, gambling den and political intrigue
-A huge damned town that acts as a trading hub, collection of stores, slums, drug dens, a fucking BANK, entire water-collection industry and more
-The Boneyard, where weapons/armor is produced, multiple factions warring between each other, and people actively working on how to build and improve what they already have
-A zombie city which has functioning water filtration and despite being inhabited by fucking GHOULS has managed more than FO3-4 cities despite most of their populace being so braindead they attack you on sight
-And of course the mutant army which is actively building mutants for an actual (if faulty) reason and actually is going somewhere
Bruh that's a dumb take, that's like saying where are all the Fiends coming from in New Vegas? Do they writh out of the mud like Uruk Hai? How come no matter how many I kill even their leaders there's still more?
You're equating generic citizen mooks (which by definition NEED TO BE WANDERING AROUND TO PROVE WE HAVE HUMANS LIVING IN BOSTON!) with generic ENEMY mooks which by definition need to spawn because the aim of the game is to shoot at them.
Fallout 1-2 managed to pull of both so I reckon with 10 years of technology advancement Bethesda can do better. If we look at FO3-4 at face value we have to assume the vast majority of humans are insane psychopaths' which wouldn't make any sense.
I mean gameplay wise it's probably because of the settlement building feature, too many NPC's would probably effect the game.
Story wise you don't see a lot of people because of the Institute, Gunners and Raiders make leaving by yourself outside a community real dangerous. It's only when the Minute Men return that people come out of hiding.
That's the issue, if the world is so unsafe you cannot walk around without almost certainly being killed, it's going to be so dangerous that even the largest communities simply WILL be sieged and broken apart within a few short years. A single squad of gunners can kill the entire diamond city security force AND citizens. Let alone what a larger force could do. So why is diamond city still around?
The Hub in FO1 has a good dozen combat-armor security guards who will kick even a well-levelled character's teeth in, meanwhile you can genocide Diamond city with a flick of your fingers after playing for a couple hours.
I mean if we're gonna point out flaws let's not forget every DLC area in New Vegas has barely any neutral or friendly NPC's
Most areas in NV DLC's have no neutral/friendly NPC's for very obvious reaons.
-Lonesome road: Full of insane ghoul mutants
-Old World Blues: Isolated and only way to get there is teleportation, anybody who IS teleported there is lobotomized and only the player character having two bullets in their skull allowed them to survive
-Honest Hearts: Lots of friendly/neutral NPC's here, even if they don't wander about because Obsidian had to use Bethesda's jank engine
-Dead Money: I mean...I shouldn't have to explain this one.