Allow the admins of the instance to enforce their rules?
Say you have an instance with a “no-NSFW” rule, for people who don’t want to randomly come across NSFW communities. Their admins could take care of the curating of rule-breaking NSFW communities without having to resort to defederating from the entire instance. This doesn’t have to be an outright block but just a filter that could prevent the community to show up in “All”.