You have these friends, right. Your friend friends–the ones you can call and make plans with. And they have their friend friends–who they call and make plans with. And oftentimes you end up doing things with their friend friends–partying, going camping, going to the beach, etc. You spend a LOT of time with their friends. So much so that you become friends with their friends.
But you never really cross over into that place where you’re independently making plans. Sometimes you do, eventually, when your interstitial friend goes away. Or maybe you never do! Maybe when your interstitial friend goes away, you stop seeing those people entirely. Both are an option. I don’t think it’s either happy or sad. My perspective is that if I want to see someone (and they have the time to be seen), then I will see them. And if I don’t, then it was because the interest wasn’t really there.