Android phones all enable RCS in the messaging app by default now.
I never thought much about it since I never really use SMS. Today though I received an SMS from a customer telling me that their internet connection wasn't working. They would normally open a ticket, send an email, or message on WhatsApp - but since their internet wasn't working they resorted to SMS (they could have still phoned if they thought it was urgent).
I replied to the SMS telling them what to try and do to get things going again and carried on with what I was doing.
After about 30 minutes I still hadn't heard from them so I checked the Google Messages app and saw that my messages hadn't been sent. Why? Because it wanted to use RCS to send to someone with a broken internet connection, and RCS requires a working internet connection. I had to manually select to resend them using SMS instead.
So the one time the SMS app could have been useful, it wasn't.