Not different departments - different COMPANIES. Disney is not one company, its a company with a lot of subsidiaries. And DVC is not related to the hotels other than being a sister corporation. Each company (each companies executive) is responsible for its own profit and loss. If the guy running hotels isn't making his numbers, he sure isn't interested in giving hotel rooms he could sell to the guy over in DVC. If the DVC guy screwed up - that's HIS problem, not the guy in hotels. Who, by the way, doesn't really like the DVC division anyway because they keep taking his repeat business and turning it into DVC members - which makes it harder for him to have growth.
Little in the way conglomerates are run tends to foster cooperation between companies - not unless there is more revenue to be made for both sides.