That may be the case where you and I live perhaps, but these countries that I speak of, have an entire ecosystem built around WhatsApp. Many companies there no longer provide a customer support number that you can call for instance, they expect you to interact with a bot run on WhatsApp, which can further lead to chatting with an actual agent speaking to them, but that's all done via WhatsApp. Also many teachers in schools and universities share lecture notes and study material via WhatsApp groups. Doctors and medical labs may share electronic copies of your reports via it. Some restaurants accept reservation requests solely via WhatsApp. It can even handle payments now, and besides using it as a means to send money to someone, some companies have even built entire e-commerce platforms around it, using interactive bots and the payment features. So for you and I, WhatsApp may be just another messaging service, but in these countries WhatsApp is quickly turning into an "everything" platform, and it's not trivial for someone to just replace it, unless they want to go live in a cave and cut themselves off from modern society.