Every time I have gotten a SIM card in a country south of the US-Mexico border, the carrier spams the text messaging. But nobody else uses it.
In the US we don't reliably use WhatsApp, iMessage is locked down, and Signal, etc., are just for tech bros or political hacks. Yet, everyone wants to text instead of call, so we are in this world where we need to make RCS work, and they are just not putting in the effort.
What I mean is that in Mexico, Brazil, and many other countries, WhatsApp is the de facto messaging standard. Businesses expect you to have it, restaurant ordering is integrated with it, etc.
In the US we don't reliably use WhatsApp, iMessage is locked down, and Signal, etc., are just for tech bros or political hacks. Yet, everyone wants to text instead of call, so we are in this world where we need to make RCS work, and they are just not putting in the effort.