RCS is pretty old at this point, almost a decade. But its also not as open a protocol as it says on the tin. Android is using a ton of extensions, notably end to end encryption, that are not standardized and the infrastructure is hard to run. Carriers are for the most part using google rcs infrastructure or users are accessing google infrastructure directly because the only relevant RCS users are android users who default to not using carrier RCS servers that don't have the google extensions. So its really an "open" protocol managed by google.[1][2] Somewhat of an upgrade over the closed ecosystem of imessage in principal but RCS isn't the open protocol win that many fantasize about; it feels more like hoping on to a product that's in the late extend and extinguish phase.
In large part because of Google's cajoling and creation of Jibe. The carriers view messaging as a software product. At this point because basically every phone is running android or ios thus supporting a lower level carrier protocol is of questionable value for them when anyone can submit an app and run their own infrastructure to support a messaging protocol.
RCS is pretty old at this point, almost a decade. But its also not as open a protocol as it says on the tin. Android is using a ton of extensions, notably end to end encryption, that are not standardized and the infrastructure is hard to run. Carriers are for the most part using google rcs infrastructure or users are accessing google infrastructure directly because the only relevant RCS users are android users who default to not using carrier RCS servers that don't have the google extensions. So its really an "open" protocol managed by google.[1][2] Somewhat of an upgrade over the closed ecosystem of imessage in principal but RCS isn't the open protocol win that many fantasize about; it feels more like hoping on to a product that's in the late extend and extinguish phase.
1: https://9to5google.com/2023/09/21/t-mobile-rcs-google-jibe/ 2: https://9to5google.com/2023/06/09/att-rcs-jibe-google/