I too could manually encrypt data and send it via regular old sms. That would require the other party to know of and make use of extra tools to be able to read and reply. If not, then they might not be able to read the message, or worse, reply in plaintext. That’s what google is doing with rcs. Rcs is not encrypted. the google app encrypts the data and sends it “unencrypted” over rcs. From rcs’ point of view it looks like “this user is trying to send random junk… who am I to judge?”