I totally buy this as someone located in the US, but what is everybody else using? It can’t be WhatsApp? Is everyone sending all their connection graphdata to Meta?

A lot of SMBs use Instagram to connect to their clients, so Instagram build-in messenger is a default option for a lot of people (especially women) in many parts of the world.

Some places have regional messengers that are very entrenched, like Line in Japan or KakaoTalk in Korea.

WhatsApp is a default option in a large number of countries including most of Middle East, parts of Europe, Brazil, most of Africa, Southern Asia. To me it is surprising, too, because out of all messaging options WhatsApp seems like the least developed and least ergonomic.

And yes, this does mean that most people share whatever data Big Tech wants. They use Meta to talk to each other, auto-upload their photos to Google, click "accept" to every cookie banner so that thousands of no-name companies around the world know where they are and what they are doing at all times.

You understand that Facebook and Instagram are also very popular yes?

People who care about privacy (very very few) use signal, everyone else uses Whatsup

in my country it's Whatsapp, and has been since before it was acquired by Meta

It’s WhatsApp. No one thinks about sending data to Meta. The world is much bigger than the HN bubble, where almost no one thinks about privacy implications.