I don't know why. They're two small little areas.Obviously the mission structure isn't there but it still does kind of feel like we were cheated out of content.
Also, you guys would probably shocked to see all the things that get cut in development. You're not getting 'cheated' of those things. There's just only so much time to work with. And its entirely possible that the foundations for future DLC were starting to get laid before the final game got released. That's also how it works with many games and there's nothing really wrong with that. Its become necessary to ensure you have post-release content that doesn't come out too late or else many people will have already moved on.