Since
DVC members are using room inventory they own, and are not booking room inventory belonging to Disney, we're not eligible for Disney promos. Free dining is only for guests paying full price for their Disney-owned resort room - it's an incentive to get people to pay rack rate for their room.
In short, since we don't pay the hotel-business part of Disney any money when we book a room using our points, they have zero incentive to give us a free dining plan.