In the US, AT&T, T-Mobile, and Verizon have slowly moved to Google’s Jibe platform after years of maintaining their own servers for Rich Communication Services
I understand that the service is not provided by carriers any more but by Google.
And they hide this information a bit further in the app.
This sounds like a problem exclusive to the United States. In Canada all of our carriers still provide RCS. Rogers was one of the first major telcoms to implement RCS country-wide for Androids prior to the major rollout elsewhere.
Additionally, RCS is a generally open standard that can be adopted by anyone and implemented by any carrier. Google only runs their RCS back-end when carriers are unwilling or unable to do so, like in other regions worldwide. RCS is interoperable and even if it's a system being used by Google, it's an open standard. Apple were the ones not allowing the interoperability here, and causing the centralization.