system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Its been 200+ years since the bombs fell. There's long established and regionally known population centers across the continent. Why does nobody clean up a bit?

I know deeper NCR territory and Vault City areas are nicer, but what about areas like Diamond City or Rivet City? They seem to have populations of hundreds if not more, so why are they so contented to live among rubble, corpses and ruined buildings for centuries? Why not get a few peeps and some trash bags and tidy up?
gpt
The situation in the Capital Wasteland is far worse than most other parts of the continent during the Lone Wanderer's adventures. China specifically wanted to kill America's government, and then poison the earth forevermore to prevent another America from rising in its place. The capital wasteland was poisoned by some of the worst nukes in China's arsenal, which continues to kill people centuries later, and keep populations low. 

Not only that, the supermutants in the Capital wasteland have forced the meager population into heavily fortified, isolated, or otherwise inaccessible settlements. Whatever progress might have been made before the Lone Wanderer escaped Vault 101, the supermutants had put a violent halt to it. Basic survival had always been the law of the land in the capital wasteland, and the supermutants only made the situation worse. 

We know, however, that after the supermutants and enclave were defeated by the Lone Wanderer and the East Coast Brotherhood, conditions in the capital wasteland have MASSIVELY improved. Project Purity still has a long way to go in cleansing all of the water in the area, but its done a huge amount of work in just a few years. And without mutants lurking around every corner, there has been cleanup efforts in DC. Enough for the Brotherhood to assert even more power over the area, and turn it into a proper capital and base of operations. Powerful enough to send the Prydwen to Boston. 

In the Commonwealth, there is one simple answer as to why people continue to neglect their wider surroundings: the Institute. Just like how supermutants made the bad situation in the Capital Wasteland worse, the Institute have intentionally kept the people of the Commonwealth divided, isolated, and afraid. Largely by unleashing a new kind of supermutant on the surface, which created much the same situation as in DC. But also by replacing influential and powerful people with synths, the surface could be kept under proper Institute control.

There were several efforts in the past to unite the local settlements and begin proper rebuilding efforts, but the Institute put a stop to it. (whether intentionally or not is up to you) But at least since Shaun has taken over as Director, the Institute has seen more benefit in keeping the surface disorganized and filthy than letting them clean up and organize. If anything, keeping the settlements isolated makes it easier to do horrible experiments on them without the wider population becoming the wiser.