Earlier quoted context omitted.
Having lived all over the world, but not the US, I don't think I've sent or received an SMS/text message once in the last decade (except for bad 2FA implementations). Apple's weird and semi-transparent (to the user) hybrid system of mixing a proprietary web protocol and SMS in the same app is obviously problematic, and the rest of the world moved on to other messaging services, but it's weird that the US is still stu…
It is a little odd that the US is so iMessage-heavy when the rest of the world isn't but IMO relying on another proprietary protocol (i.e. WhatsApp) really isn't great either. I kind of think everyone is in an awful place.
It's not odd at all.
Lots of iPhones in the US because of high incomes, and high iPhone availability. Lots of non-iPhones in the rest of the world because of comparatively low incomes, and significantly less iPhone availability.
I see no mystery.