Hi and welcome to the Google Messages Community.👋
Never as there are two flavours of RCS, one is a general flavour which is what Apple is building on to support RCS which message applications are free to do the same with.
The other is proprietary which is Google's flavour.
Did I mention that both flavours don't talk to each other? Which also leaves mobile service providers stuck between a rock and a hard place.
Google's flavour of which only they and Samsung* use is a little more exclusive as you can see...........
*Samsung has a special deal with Google to be able to use it.
So messages application are free to build their own implementation of RCS but it won't work with Google's implementation.
Thanks for your question.