I can't imagine that this is actually the reason. SMS has long been replaced by iMessage, WhatsApp, Telegram and similar services. Nobody uses or values SMS the

I can't imagine that this is actually the reason. SMS has long been replaced by iMessage, WhatsApp, Telegram and similar services. Nobody uses or values SMS these days and the carriers know it, which is why the service comes free with pretty much any (european) contract. So if messaging already happens outside of the carriers' reach, why would those carriers be upset if Google added another entry to the list of services that have replaced SMS?