I'm in WhatsApp groups with friends who live abroad, SMS is not an option. We could use another chat app, but then I'd have to convince every friend from every group to use something else. WhatsApp is what every friend I have agrees on.
I belong to several hobby groups that exist only on Facebook or Reddit (or Discord, but I dislike it for several reasons). I'd like to ditch both Facebook and Reddit, but that would mean leaving those hobby groups, and given the joy they bring me, I'm not willing to pull the plug yet.
So you see, it's really not that easy.