They certainly could. When the dining plan first came out, it wasn't available to DVC. Generally, the ability to add dining plan/ME is added on the CRO side first, and released, then added to the DVC side. I'd bet its a systems release thing - they do the development with the CRO systems and since the DVC systems are a separate integration, we get added later. I've long been of the opinion that if Disney wants to put a dent in the
DVC rental market, they make ME and the Dining Plan only available to a room booked in conjunction with a member stay. (i.e. if you book two studios and are staying in one, both get benefits - if you let your son use your points while you stay home, he'll need to grab a cab from the airport and pay OOP for meals).