The transition of the major social networks over the last 10-15 years -- from being a space for friends to interact to being a space to consume content produced by "unconnected" entities like influencers -- has created a huge opening for someone to claim the friends and family network. There is no one better positioned (at least in the U.S. where iPhones are the majority handset) than Apple.
WhatsApp has like 99.9% market share here and I assume it is a lot bigger than anything else in the EU too.
I wonder why is that though. Everyone around me has an iPhone basically and I haven’t received a blue bubble in years. The messages app is not even on my home screen.
Then when the same iPhone app seamlessly started sending iMessages (blue bubbles) to other iPhones rather than SMS (green bubbles), people just kept using that.
I see this listed as the reason often but I had unlimited SMS then too. In fact I remember visiting the US in 2009 and I was charged to send AND receive an SMS which was a shock.
I think the actual reason is that communication across borders in Europe is very common and those SMS's were not included in the unlimited plans as they were messages abroad. So they were subject to fees (usually high ones). I think this is the reason it was common - especially given how common it is for students to study 'abroad' in other European countries. There were a few competing apps for this at the time (Vibr I think was another but was more call focussed) but WhatsApp won in the end.