Mine is set to "All Friends" except "DoNotShow" and there's about 3 people on my "DoNotShow" list.
Have also excluded family for a few posts.
IIRC, Facebook never really promoted those features or tried to make them easy and intuitive to use. Recently they've also made changes to make them less useful.
It's sort of like difference between having a well-designed and usable feature or a similar feature that only exists to check off a checkbox.
I remember Facebook having it first; this blog post (https://jessicavitak.com/2011/09/01/facebooks-circles-how-to...) confirms that.