That is only with v3.0, but the reason for including MMS in v1.x or 2.x to the non-AT&T carriers does look to be Apples fault. It certainly doesnt seem technical.
Of course, we have no idea what silliness was in the initial contract between AT&T and Apple that reportedly was for 2 years. MMS did appear in v3.0 right after that speculated timeframe would have ended. Maybe there was some wonky wording that kept Apple from offering features to other carriers that AT&T couldnt match.