Yes, most people are using whatsapp because it was one of the first to use phone number as account handle and to dig into your contacts to find. No risk of mispelling a complicated account name, auto discovery + group chats. The rest is inertia helped by the additions of features like voice messages, video calls, stickers way way way before encryption in order to stay current with the competitions.

If you ask most people how can they be sure that meta is really encrypting end to end, most shrug off saying that meta already knows everything about their lives through FB, Instagram anyway.