I'm guessing most of what we saw was done for awhile and then cut and chopped up into dlc by activison. To accommodate these changes the story was probably removed along with several other things...I mean it was confirmed that Peter Dinklage recorded way more Ghost dialogue than what we saw. That's the reason so many people have left. They saw their work bastardized and Bungie shouldn't have made the deal they made, but those guys left in charge are bastards for sure. They let this happen and they are ok with it.