Well, I think most people have friend systems. Just not quite as brutal.
If you invite someone and they bail 10 times, maybe you stop inviting them.
I am pretty sure certain events I’ve been invited to was only because I was good friends with someone else. And once they stopped going my invites stopped as well.
Some people you’re close to may have other things going on in their lives, but you loop them in anyway for when their situation changes.