Comment by watusername

It used to be kind of distributed, but Google has been strong arming carriers to use their hosted Jibe service through a combination of proprietary extensions (e.g., E2E which is finally standard) and bypassing carrier control (if the carrier didn't provision RCS, Google Messages would use their own service iMessage-style).

From the end user's perspective, if the carrier didn't use Jibe RCS, it simply wouldn't work well.