The idea of making Apple use it is also part of Google giving the operations to carriers, just like SMS, and then gradually replacing SMS altogether. Google isn't even supposed to be running the RCS servers. But they did it in order to get the standard up and running everywhere. It's an open standard, and multiple carriers in several countries are on their way to carrying the burden of the servers, the way the standard is supposed to operate. Once it's operating, all servers can talk to each other, just like you can SMS a person on another carrier line. RCS will allow universal rich texting.

Surely XMPP and other standards are different and I would prefer any other than something championed by Google. But the truth is, that the other standards aren't invited to sit at the right tables and don't offer the same “replace SMS once and for all” potential the way RCS does. XMPP for example is super expensive to escalate and like almost all of the traffic is just presence messaging, which is super wasteful and energy intensive on servers. RCS is not the best, but it's one that all carriers and telecommunications agencies are on board for replacing the archaic SMS. And it doesn't preclude using other protocols. Like, WhatsApp, Signal, Matrix and Telegram will still continue to exist.