[out_of_protocol]

e.g. you can't send rcsmessage if target telcom does not support it (fallback to sms exists but that's runis the idea). Since adoption is (almost) always s-curved, last gsm operator to adopt it will do that ... not anytime soon

[hpaavola]

Which means that at its worst, RCS is just SMS. Which is an argument for RCS replacing SMS.