You're running into multiple issues.

One is that everyone forgets who actually decides the rules for a given C/. This happened all the time on reddit. The mods make the rules, period. That's how lemmy is set up, though admins have veto power of course.

Since whoever creates a community is the top mod, they get to decide what the usage of the sub is.

When you have an umbrella term like politics, news, knives, cars, users come into it with their own preconceived assumptions of what that C/ should be about. Often to a degree that shows their arrogance as much as anything the mods do. It was a long running battle on r/edc with people thinking their definition of the term was the only acceptable one. Happened in morbidquestions all the time too.

But the hard truth is that no forum can be a bottom up organization unless every single person using it inherently thinks in that cooperative way. And that is impossible. The only way you could make a C/ where every user is in perfect agreement about the rules and usage is to have it set up by the group and closed to outsiders.

Now, you've also run into the language fallacy. You've forgotten that an forum with a name in a specific language is going to be predominantly filled with things in that language. You aren't going to find many news reports in Korean on an english based C/, and that's the majority of internal news about korea.

English is currently the ironic lingua franca of the world, but there's still only a handful of countries where it's the default. So, on a news or politics C/ with those words as the name, you have to expect a majority of the posts to be from or about those countries.

With that in mind, you have to remember that reddit was predominantly american. Most of these newer communities here were started by r/efugees, directly carrying over the names of subs. Most of the users looking for those C/ names are also ex redditors looking for the familiar. They'll be american, posting things about american news and politics.

Since the "owners" (really head mods, but you know) make the rules, and they've decided to limit things, there's really nothing anyone can do unless instance owners step in. And what's not actually something we want happening very often.

I don't think it's arrogance. It's just habit and familiarity.

Now, do I think that anyone running an umbrella C/ should be aware of that fact and not artificially limit things to one facet? Hell yes, the rule is a bad one. But it ain't my C/, and it's a big fediverse where we can have !news in fifteen different places, run them as a proper umbrella community and let the users migrate wherever they prefer.

This isn't reddit. It's nigh impossible for one person to squat a C/ name at all, much less on every instance.

Shit, afaik, there's no rule against setting one up and actively notifying users on C/ twins on other instances. There's a shit ton of people that will be very happy to subscribe to both, or a dozen. None of "my" C/s have duplicates currently, but anyone that sets one up is more than welcome to advertise the fact politely. Hell, if they bother to let me know, I'd link that shit in the sidebar.