real world social networks have agency if you define ephemerality as agency. It's an accident of digital platforms that nothing is ever forgotten, not a feature inherent to normal human relations. In the real world you drop phone numbers, you forget events, unused relationships atrophy. And that's not a bug, forgetting is a feature. For anyone who isn't convinced of this, Black Mirror did an admirable job in its first season putting the pathologies of social technologies on display that record everything.
It can be argued that humans actually hate forgetting things. That's why we invented writing. Spoken language lets us share arbitrarily abstract thoughts with others. But human memory is imperfect, so spreading knowledge or memories through word-of-mouth is unreliable. Writing lets us preserve that information as intended by the original author, potentially indefinitely. That's also why we always wanted to be able to record and play back what we hear and see, and our civilization only fairly recently, in terms of history, got advanced enough to have technologies to do that.
>It can be argued that humans actually hate forgetting things
I agree with you, I don't even think that needs to be argued, we without a doubt hate forgetting things, but we also hate eating our vegetables. We do hate a lot of things we probably shouldn't. We are perpetual hoarders, as a species we have the bad habit that we're not very grateful for the problems we don't have as a consequence of things we don't keep. We're not very good thinking in terms of absence.
That's why Marie Kondo sold a ton of books and got a great Netflix deal simply by teaching people how to throw stuff into the garbage. Civilization is great at record keeping but not doing too well on the social bonding front, or in the words of George Carlin: https://youtu.be/MvgN5gCuLac
https://en.wikipedia.org/wiki/The_Entire_History_of_You