Earlier quoted context omitted.
It’s comical that all of the replies to what you’ve written claim you’re wrong, because you’re actually 100% right. And this is even more true when you remember that the company had fewer than 20 people for a long time, and that there was only one real goal , that seems to be forgotten: they needed to clone BlackBerry Messenger and get it working on every platform possible. That was it. That’s all they needed to do,…
Also can't overlook that for many SMS was ludicrously overpriced, but the early basic smartphones (palm and symbian) often had wifi capability; WhatsApp provided secure, ludicrously cheap instant messaging across all meaningful handsets. And that's all it had to do; the telecoms weren't interested in making SMS cheap or secure, RIM didn't want BBM on anything but their devices, ICQ/AIM/MSN/etc were similarly unavaila…
You can scrap secure from this, the vast majority of users don't care or even know what that means.
If SMS was more secure I 100% would still expect whatsapp to win. Convenience and cost are the biggest drivers here.