But what would prevent people from using WhatsApp to talk to businesses and Signal to talk to friends? I have been using multiple channels with friends forever: phone call, mail, email, MSN Messenger, Facebook, IRC, ICQ, WhatsApp, Threema, Signal, Slack, Discord, Matrix, ... What sucks is when I can't reach a friend. But I never saw it as a problem that I had too many choices to talk to them :-).
I don't really understand this "It has to have 100% of the market" stance. I don't want monopolies, I don't really understand why someone would say "this monopoly sucks, but I really want a monopoly so I won't ever change unless it is for a better monopoly".