I have three friends from high school that I still keep in touch with. We have a Whatsapp group that isn't super active, but we chat once or twice a month there. Even though we all live in different places now, we meet up roughly once per year, for a few days, to see each other and hang out, and our chat traffic jumps in frequency for a couple months after that meetup.

I have three friends from college that I still keep in touch with. We have a Signal group that's a bit more active than my high school friend group, with weekly activity. In-person meetings are rare; two of the friends have larger than average family obligations. In college we originally bonded over scifi TV shows, and when new episodes of some shows we all enjoy come out, we'll try to do group watches of them on Zoom (usually with a general chat/hangout before we start watching).

I have three friends from a previous job that I still keep in touch with (I have other friends from this same job that I still keep in touch with and see often enough, but this particular group struck me as a true "friend group" and not just a random collection of people who sometimes see each other in various combinations). We have a Slack workspace that was originally created for one of the guys' bachelor parties in 2018 (this is the only all-male group out of the three). Two of us still live within a ~30 minute drive of each other, but the other two have moved away. The Slack is very active, with near-daily activity, even though one of the four of us lives in a drastically different time zone now. In-person meetups are a bit more informal (and rare for the one of us who lives across the world); often it will just be two or three of the four, depending on who is visiting someone else's city at the time.

While I'm not involved in the day-to-day lives of these friends, they are still dear to me, and maintaining these connections is important to me. I guess it's important to all of us; in the past I've been a member of group chats where there are one or two people who never participate, even though the others do regularly, and it always feels like a bummer to see their name in the list but never hear from them (the former co-worker group I described is like this). It's a tough thing, though, when you think about it: to make these sorts of things successful, the friendships need to be of roughly the same importance to everyone in the group, and I expect that's a difficult bar to meet sometimes.

The friends that persist beyond what you describe are because we invent some shared project to work on together. Really doesn’t matter what it is.