They don't want you going to outside vendors for food because it affects their negotiations with the arena owners.
Vendors inside the arena say they are unfairly left out when the agreement between the Society and the arena authorities says inside vendors can't open shop during the DC. But then these same vendors see JWs go to outside vendors for lunch and complain. So the Society 'solves' the problem by barring JWs from going to outside vendors. When JWs go anyways it makes the negotiations for the arena more difficult for the Society.
It works the same way with the hotel lodging list.
Everything the Society does/negotiates is mainly in their own interests, but spun to JWs as an obedience issue and as something done for them.
Bobcat