The problem with rcs is that it needs to work without a data connection like sms. For that to work, every single mobile operator needs to support it and route it. For that to work they need to work together. The problem is they don’t and there are different implementations, some don’t support it at all. Even when they do, the phone needs to support it. Google is now at a point where they have rcs capable messaging on every recent Android version. Apple is now also integrating rcs into iOS. They are circumventing the operator problem by enabling rcs over wifi or your subscription data. But that’s a workaround, because it requires data, while sms just requires a cellphone signal. Until operators start working together to enable and relay rcs messages, Google and Apple habe the monopoly by having rcs routed directly to their messaging apps over the internet instead of directly to the device like sms does.