Because the technical part has been solved for a while and this has moved into being a social problem. My kids only use iMessage/SMS for people over thirty, and use Snap with all of their friends. In family groups, you standardize on on whatever. Most of my extended family decided on FB Messenger a while ago (I don’t participate, but my wife does and can fill me in.) My immediate family just uses iMessage. Friend groups I’ve seen generally do the same. They pick Telegram or WhatsApp or whatever, and then the quilting club just uses that. This also seems a very US centric issue - basically everywhere else is either on whatsapp or Line or WeChat or whatever.