I don't know, WhatsApp won my local market decades ago by not having to pay 10 cents per message. People didn't really care about encrypted chats until maybe ten years ago, and even today millions are using Telegram for their every day messaging. No idea what the security situation of Vibe and Facebook Messenger are these days, but their numbers also exceed the hundreds of millions together.
We're stuck with iMessage, which Apple is actively hostile towards non-users. Even for me, who had an iPhone, it was a royal pain in the ass. What do you mean I can't see my messages online? I need a Mac? Are you fucking kidding me? I'm a paying customer, why am I being nickled and dimed?
That, and then SMS MMS. Which are so unbelievably bad they're basically worthless.
I shouldnt have to spend 2.5 thousand dollars to get an acceptable messaging experience. I shouldn't. RCS isn't really helping, but the situation is absolutely NOT for the better IMO.