Yeah, so... no, that's fanboy stuff. That's not how massive corporations make their decisions, not how artists make their decisions and, very specifically, not what is actually in the show.

Plus of course what you're saying is different to the online panic about NV "not being canon", which Bethesda has now explicitly denied. The NCR very much exists in the show, it's just been significantly downsized to early Fallout levels. Not because Bethesda is "diminishing the creations of everyone who isn't Bethesda", though. If I had to make an educated guess based on how reality actually operates, I'd assume it's because Lisa Joy and Jonathan Nolan wanted to make a show about a postapocalyptic wasteland and having a democratic government that has been running mostly fine for the past 100 years kinda gets in the way of that.

So yeah, welcome to franchising, where war never changes and neither does the status quo. It's mostly absurd that people in Fallout are still roaming around in reclaimed pre-war gear and doing the Mad Max schtick five generations into the postapocalypse, but Fallout gotta look like Fallout, so Fallout will look like Fallout until Fallout stops making money, at which point it will not look like anything anymore. Yay capitalism.

Hey, wanna know what they'll do to New Vegas? They'll probably do some variation on the plot of New Vegas. Mr. House and the Legion will probably still be around in some form despite it not making a ton of sense in continuity. Just like this season was all about leaving a vault to look for your missing dad, just like Filly just happens to have the same layout and landmarks as Megaton, just like there's a Dogmeat and just like Vault 33 now needs a water chip and will probably have to send someone outside to look for it. Because it's recognizable IP and recognizable IP has to be in the show so it can be fueled by recognizable IP.