The US seems to be the only place where everyone uses iMessage, so Android users have to use SMS and suffer the bizarre shaming of the green bubble. In most countries outside the US, WhatsApp seems to be the default. SMS is just legacy 2FA messages, and various other transactional messages like parcel delivery notifications.
I'm guessing. Though I'm in the US but also in grad school. With a large number of foreign students there are similarly a large number of WhatsApp, Telegram, and WeChat users. I suspect this problem is very Americentric. India was able to get all its old people to use WhatsApp and multiple apps, I think there is a bit of an overreaction going on here. You'd think the world is ending for a feature most people didn't know existed (despite it being a prompt during signup).