Because taking any of those services into use requires you to take those services into use. RCS requires no action from the user. That's why. Before you ask a question, please spend 15 minutes thinking about the answer.
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
