I don't know how much Apple has to do with it, I think most of the problem is that SMS is hot trash and nobody seems too concerned with getting a replacement out network-wide (if AT&T said that they were getting rid of SMS for RCS, Apple would build it into the phone. But due to the fragmentation of the current implementation(s), nobody seems too concerned).

Most people don't think about that, they just think green bubble bad, blue bubble good, but this is one of those rare instances where it's actual technical issues causing the hangup.