I mean, these communities do get created when someone feels like there’s a reason to. There’s just no council or whatever regulating when and where a community gets to be created, so any user on any instance can decide to open up and promote their community.
And frankly, I have no idea what the precise effects are. When you subscribe to all of these, it won’t really be much different from just one big community in that sense. It may mean, though, that someone new accidentally joining only one of the communities will not be presented all the content they want, yeah.
On the flip side, having it split is kind of cool, because you can decide to only subscribe to 2 out of 4 communities, if you only want half as much of this content in your feed. Or you can decide to subscribe to all of these, but not to the one on angry-instance.net, because you don’t like the tone of the discussions in that one.