Probably very few if that’s what their friends use, but that doesn’t mean they don’t resent it.

A billion people might use Facebook, but 1.3 billion use iMessage. I think this is a significant risk for services that don’t respect user privacy.

I call bullshit on more people using iMessage than any of facebook related services. In this case, I feel like you've a very North American point of view. Majority people who have a smart phone has one of fb/whatsapp/instagram accounts, while iPhones don't even make up for the majority of market share when it comes to smartphone.

Huh, that's interesting. I'm a Brit with a Chinese wife and spend a lot of time over there as well, so I'd hardly call my views America centric. There are a dozen countries I've spent more time in than the USA. It is possible I have a geographic bias, Facebook is barely a thing in China.

But China is an exception. This link says Whatsapp has 1.5 billion active users!

https://www.businessofapps.com/data/whatsapp-statistics/

That's a bad metric. I find Facebook a privacy disaster (and user hostile and i am less happy when I use it). But am I willing to delete it? No, because if I meet someone I can friend them on FB later, and it's my only means of communication for some people. If a better communications network were available I would switch, but since there isn't, I can't.

There you go, you find it to be a disaster but you still find value in it. It's benefits outweigh the concerns you've. IMO it's actually a metric that shows how many people are actually willing to give it up for the sake of privacy.

How does having these apps on my phone hurt my privacy?