I think the original use case was for physical communities. The fedimint is multi-sig and would have 3 keys that are held by 3 different respected people in the community. Would mean that rugging is far less likely to happen.
It allows a community to have their own circular economy while also allowing people to cash in or out.
I don’t really see the point of them for online communities aside from privacy.
Externally, all that gets seen I think is a lightning transaction IN to the fedimint and then the transaction back out is blind? Not 100% but the idea was that it was harder to analyse lightning transactions I think