They tried to make a bazillion messenger apps, all of which failed, and now they try to piggyback on an existing standardized protocol but don't expose any APIs for other apps.
While at the same time pushing this "Apple is bad because green bubble" narrative because Apple doesn't support it. It's somewhat amusing in some ways. Companies (Google or Apple) are never on the consumers side, and yet we fall for it all the time.
If you need to actually send files etc use another one of a multitude of messaging apps out there including the latest Google TalkMsgChatThing (but it works)