#Mastodon trust and safety people, I need your help

I'm trying to understand how "Quiet Public" is used. In nearly every UX discussion I have with people the vast majority not only don't understand it, but it actively confuses them.

That doesn't mean we shouldn't have it, but I would like people to at least know WHY we have this. Given you can already opt out of search results w/ a setting, why you wouldn't just use "Followers only" instead?