The niche community thing, totally. I can count at least five different apps on my phone, each for a single community (neighborhood, church, kids sports, kids school, family, etc). In the future I might still have the same number of apps, but they would all use the nostr protocol and allow me to use the same account for all (if I want).
Discussion
Yes, and the apps could be more tailored to the needs of the group. I'm in a few FB groups just because "everybody has FB," not because FB groups is the best structure for the group.