It is intentional on Apple's part. Yes, MMS has significant restrictions. But those restrictions only apply for Apple users if Apple forces the their users down to that level. The iOS Messages app is software and as such can do things to to work around the restrictions presented to their users. They could, for example, send all group messages traffic through iMesaage ( full resolution images/videos, typing indicators, etc) for all iMessage users, and also create MMS message group for all non-iMessage participants, but hide that from the iMessage users. Any incoming MMS messages from iMessage capable users would not be presented to the user (because they already got that message through iMessage). That would enable everyone to communicate together, but not restrict the features of the iMessage capable clients. Apple has had 2 decades to do something like this, but they've CHOSEN not to.