It’s automatically replacing SMS when texting iPhone users and supports plenty of modern features like group chats, embedding media etc. iMessage has an actual stranglehold in the US where teenagers have to use it not to be left out from their social circles (group chats are pretty much broken for anyone not using it). So called green bubble (SMS) vs blue bubble (iMessage) puts pressure since it’s a bit of a status symbol too.

If the same was happening in the EU it would make sense to scrutinize it under new regulation. I’d wage 90% wouldn’t notice if their messages were delivered as plain SMS though.