This is a recurring type of comment. Some people use primarily WhatsApp or FB messenger. Other people's entire social network is on iMessage. Neither talk to us

This is a recurring type of comment. Some people use primarily WhatsApp or FB messenger. Other people's entire social network is on iMessage. Neither talk to users of Signal. And there are also separate groups of people who think everyone is on Telegram or WeChat. Clearly there are network effects, and which app wins is varies between regions and groups.