I’m not sure it has a name, but proper scaling of communities. There are lots of niche communities that get no traction because they are so small. The subscribers should be using a more general community to gain interest and branch off only once that topic reaches critical mass.
I wholeheartedly agree. There are so many communities that seem to be created just for one specific post and then remain empty (most commonly for games or shows from what I've seen). Instead of building up a more general-purpose community of interactions, the result is a lot of fragmented ghost towns that are far less than the sum of their parts.