Why is northern Eriador (Lake Evendim, Fornost) deserted at the end of the 3rd Age?

[CSteefel]

I am wondering why the northern portions of Eriador appear to be completely deserted at the end of the Third Age. I am thinking of Lake Evendim and Fornost, which really are not all that far north of the Shire. Other regions seem to be deserted as well, including the land between Bree and Rivendell, even south of the road.

I have seen a reference to the fact that the Rangers occasionally go up to Deadman's Dike, but the reason for this is not readily apparent. Only thing I can think of is that most of this land is "haunted" in some way or another by the Witch King 1,000 years before and it took the downfall of Sauron to make it possible for Lake Evendim to be resettled in the 4th Age...