Yes, but there are also plenty of countries where mobile data or even smartphones aren't nearly as universal as they might be in the places where most people use whatsapp. There, people use mostly SMS and phone calls. Whatsapp and the like are the thing you use when SMS/calls would be too expensive, so international.

Both of these exist, as do middle grounds between them.

I'm in only one WhatsApp group with someone local, everyone else in my chats is from abroad. Yet I'm from a country with dirt cheap data and nearly universal smartphone ownership. People just don't use WA here for whatever reason. But drive an hour across the border and suddenly everyone is on WhatsApp.