alt Hacker NewsWhatsApp happened at a time when, in Europe, you paid for SMS.
WhatsApp allowed people to send SMS without paying, or rather, paying just once to buy the app, so it was instantly valuable if you just convinced your spouse or parents or a single friend to install it.
To overcome it now, you need a lot more effort (or rely on enshittification, which I'm sure will happen).
No, before Whatsapp, people were mostly using Facebook messages, at least where I lived at the time.
And no one was paying per SMS at the time we were using SMS for communication, almost everyone I know were on monthly plans that gave you N text messages and N minutes of calls for static sum each month.
The first people I saw who started using whatsapp, was people who were communicating across the border, because even if you had a monthly plan, those didn't include international messages. Eventually we all converged on whatsapp because that's what outside family and relatives used anyways.