Doesn’t rcs depend on having mobile data or internet access on? If I understand it right it is strictly worse than sms.
Many people just have data off most of the time and sending messages with the system app assumes things are delivered immediately and everyone easily receives them. If you forget your data is off or don’t have internet for a while then you end up assuming people received stuff when they didn’t.
All phone isps have basically unlimited sms for free when data is paid in huge amounts of gold.