Those houses were most likely made by new people to the server, and may have been their very first trek out into the wilderness. A new player has no place to store what few items they have, and so you can't expect them to travel too far from the spawn. I myself started off living in a small ruined hut in Old Caerdia very close to the "To the North" warp. The fact that these houses are griefed, I assume that these houses were not made with valuable blocks (as evidence by the cobble and planks on the rest of the structure, and also assuming new players don't have treasure blocks to place as walls) and were probably torn apart by other new players needing materials to build little places of their own. These new players may also be attacked quite frequently by people, and so eventually are forced to move farther away, most likely leaving whatever structure is left behind.

 

Point is, restoration around spawns is nice, but don't expect it to last long. This is what will naturally happen to areas around spawns.