Opening up my "messaging apps" collection on my phone shows:

- WhatsApp (sees the most use by far)

- Facebook messenger (almost completely phased out, used for maybe one or two people and to regain contact when a phone/number is lost or changed)

- SMS (one or two people, some spam advertising I never get around to unsubscribing to, and number verifications from signups)

- Gmail, Outlook, Protonmail (mix of work and personal emails)

- Telegram (one or two people)

- Skype (mostly work contacts, but some personal)

Also an honourable mention to Instagram, which doesn't live in that folder but does house a few of my conversations with people.

I don't have any trouble associating a person with an app or apps, and occasionally will have different conversation "threads" running with the same person in two different mediums.

The only real difficulty, in that case, has been when I've needed to remember where something in particular was mentioned.

That's not the issue.

Those are mostly run by immoral companies that feed of your privacy.

One is bad enough, and none works for all. Except for sms.

It is not a hard choice to make.

I'm completely aware and in agreement on the sad state of the companies who manage those apps, and the transition that the various relationships have taken and are taking is from bad to better in that regard.

But I regularly talk to people from, at a quick count and including the EU as one because of the telecom rules, around 4 different countries. My circle of friends and colleagues travel frequently, as do I, and I don't want to have to think about where they are or I am before sending a message.

SMS is entirely inadequate for my usecase. It would cost me a fortune.

Sure, but that is an edge case.

For others the choice of sms is not surprising at all.

I don't. I expect them to sign up for any other service of their choice for themselves. I personally find SMS infuriating -- what I find surprising is that most other people don't seem to hate it as much as I do.

Most other people use IP based messaging because it's a much better experience. SMS are a thing of the past with a few exceptions. Banks and Visa insist sending 2FA codes by SMS, people with old phones must use them, I do use them in emergency (no data connection.)