Edit: looks like I was wrong. I'm in the Netherlands. In the Netherlands and our neighbouring countries, Whatsapp is ubiquitous, so I presumed the rest of Europe was the same. I guess this proves that assumption is the mother of all failures.
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.
Latin America is basically WhatsApp and nothing else.
https://www.messengerpeople.com/global-messenger-usage-stati...
iMessage and Telegram covers everyone I know.