Shit happens, you might have crunch at work for some time and spend much less time on social activities in that period, which means that you loose contacts with anyone but close friends. It requires conscious effort to leave that state. And there are different types of social connections, there are those where not much happens for some time, but then in very short period of time A LOT happens. That is the case for some of my friends that don't live in my city.

This is a weird take.

I have friends I've known for decades, some of whom have moved to different cities, different countries, different continents even. I don't talk to them regularly - we all have our lives and it's easy to get caught up. It's not that these people don't matter, just that we're not as close - physically or otherwise - as we used to be. Many of these people, if we did meet again in person, we could pick up exactly where we were as if I'd only seen them yesterday.

I don't use a system like this. But it's bizarre to say that just because someone hasn't spoken in a while that they don't actually matter

The thing about parsing your social network down to just a tiny group of close friends is A) it makes it harder to develop more close friends, since friendship tends to work like a funnel where you start out shallow and become better friends through time/exposure, and B) eventually you start to lose friends, whether to physical distance, falling out, life events, and eventually death, and if you only have a tiny group, it's easy for the bottom to fall out of your friend group entirely.

I've watched this happen with a lot of older adults I know, which is one of the reasons I've deliberately made some efforts to keep a pool of shallow friendships. Some of them have already deepened into actual friends, some fall off and that's ok, because that's kind of the point. Casting a wider net is part of a strategy to not end up in my later years with 0-2 total friends in my life.