In Spain in fact it's ridiculous - surveys show approx 97% of the population saying they use it regularly (https://www.messengerpeople.com/global-messenger-usage-stati...).
https://english.elpais.com/elpais/2015/02/16/inenglish/14240... has some interesting background on why. I suspect also the fact that Latin America tends to use whatsapp quite heavily (https://www.messengerpeople.com/global-messenger-usage-stati...) probably makes a difference too.