Earlier quoted context omitted.
This is so strange, no one in my social circle uses WhatsApp or has ever asked me to use it to talk to them. It’s all iMessage, Snapchat, and a growing group of people on Signal.
Messaging clients tend to be regional. WhatsApp is massive in Europe. From what I gather WeChat is dominant in mainland China but Hong Kong still used WhatsApp (though I think they might be coming round to Signal?) and the US, who have a higher ratio of Apple users vs the rest of the world, tend to use iMessage a lot more.
You're completely right that messaging clients is regional, but it's even more regional than just "Europe". I'm always confused when people claim that WhatsApp is huge in Europe, because I know literally only two people who use it. They only use WhatsApp because they have friends outside Europe.
I think we need to think in terms of single countries when talking messaging apps. Again take WhatsApp. Pretty big in Germany and Spain, but almost non-existing in Denmark (who instead rely more on Facebook Messenger or iMessage).