They support SMS as the standard carrier-supported messaging protocol (in the states, not sure globally). They also have a private protocol for apple devices which they fully own and control. And they have now announced that next year they will be supporting RCS, the next-gen carrier-supported protocol.
I think it's fair to say that Apple has been slow to adopt RCS - but I don't think that makes them the bad guy.
(SMS is insecure, iMessage is a lock in that they use to their benefit, RCS has been on Android forever, etc etc etc)