I'm sure there are dozens of people in Germany who actively prefer iMessage but I haven't met one yet. Whatsapp achieved pretty much total market capture here back when SMS still were costly and the network effects that arose from that are among the strongest I've ever seen. I'm pretty sure if someone was to do a survey, almost everyone would say Messages is for SMS only and I think most of them wouldn't know it can do more than that.
Yet i write with most of my German friends using iMessages because its automatic and i dont have Telegram or WhatsApp because nobody uses it in my european country.
