Why would I want to use RCS?
If I want to send a "rich" content message, I use Signal*, or sometimes email.
When I just want to send a basic text message, I use SMS.
When my doctor wants to remind me about an appointment, they use SMS; when my financial services providers want me to authorise a transaction, they all use SMS; and so on. Absolutely none of these interactions would be improved by making them "rich".
Also, I suspect that RCS would use my "data" allowance rather than the unlimited SMS messages included in my monthly account fee.
So, I ask again: Why would anyone want to use RCS?
Perhaps if the annoying Doctors and hairdressers and other appointment SMS stuff would use RCS, it would be better since the reply would not be to a short code that usually is not free from your included unlimited SMS, and if you are on kogan and similar providers cannot reply to anyway.