> If their friendship relies on you installing an app on your phone, that's a very shallow friendship isn't it?
This argument doesn't make sense. You can't just ignore practical aspects entirely and justify it with a cheeky "if they're truely your friends they'll accomodate ahah".
Sure if I want to send a private message to a friend I don't care whether its via SMS or whatsapp, but if I'm in a group chat with 5 of my friends I won't send a transcript of the conversation to the one person who doesn't participate.