Not that I completely agree with it, but I believe this is a move similar to the Attune changes made earlier this year. Nearly every quest item in DoF is No-Trade which shows an obviously deliberate move that direction. Perhaps they didn't want people who hadn't paid for the expansion to be able to have items from the expansion. Perhaps they wanted to encourage more people to take part in the quests and experience the content. Perhaps they are again attempting to control the economy by limited the number of items which can be sold on the market. Perhaps they are trying to promote T6 crafted items by preventing a flood of quested items on the market. More than likely it's closer to most if not all of the above. In any case it's obviously done on purpose.
As a side note completely off topic... I LOVE your siggie Lahash. That's awesome 