> People will just adjust to send you sms or call you instead for important information.

Or they won't and you will be left out of things.

Not even out of malice! Obviously your closest friend and family will adapt and keep you in the loop. Bigger looser groups are more dubious. I'm a member of a book club for example. There are of course the scheduled meets, organised well in advance. But also sometimes someone just feels like hanging and posts a message on a whatsapp group that they will be at this or that location and whoever is free is welcome to join. Schedules don't always permit it, but when it works out it is fun!

Now of course if someone from the group so want to meet with specifically you/me they will remember to send a one-on-one message, but there is a power in the broadcast nature of some of these things for organisation.

In my experience this is not true at all, especially in huge groups. I was participating in a co-housing project and after a few weeks the obligatory WhatsApp Group was forming. Immediately some people refused to join and proposed Signal / Threema instead. End of the story, the WhatsApp Group is still alive and the biggest of them all. If you are not part of it you will miss important information. Sometimes it gets forwarded to Signal but it is a rare occurrence.

It only works reliable for messages directly addressed to a person. Then people remember, oh he does not have WhatsApp. I will tell him via signal.

I complained that a sailing club I was a member of used Facebook to organise the weekly activities. They offered WhatsApp as a compromise! It was almost impossible to participate without it, because you needed a safety boat operator on site to sail. In the old days I guess they simply agreed a rota, now everyone is 'too busy' to do that, so a Facebook group is the answer, 'anybody sailing today'.

Anything involving a group is planned through WhatsApp here. It’s also used to push information to large group of people. It’s my main source of news about my extended family and how I learn about spontaneous after work gathering for example.

If I leave these, people are not going to reach out to me about them. I will just cast myself as an outsider and will be left out of the loop.

> People will just adjust to send you sms or call you instead for important information

That's a big leap of faith.

This is what I call a load-bearing "just". People don't "just". Getting people to change their workflows and habits is difficult. And they certainly won't do it for the single person who decided to opt out of common communications channels. It'll be up to you to actively maintain that relationship. After all, you're the one that opted out of the social contract.

I've encountered this everywhere, even with myself. I'm bad at keeping in touch to begin with. Anyone decided not to use normal means to communicate with me are likely to get missed among the hundred plus other people I know.

I'm not on Facebook, so I'm left out of the majority of my family's communication. The only reason I know anything is I regularly call my parents to get the summary. (It's also a good excuse to call. We always have something to talk about.)

That isn't true, but it's more than that anyway. Even if I don't use any fb service, my friend circle does, and that is enough for fb to build a profile on me, without my consent.