well not sure if the developers gave much tought to it, but contrys / civilisations do dissapair in the world.. like persia and the sovjet union etc..
and theese are just little villages, so it culd easily happen that Old camp / huntington got attacked and burned to the ground, then the survivors moved to another village / started to build a new one.
I personally dont mind that they have came up with new villages, the easy way out whold be to just randomly name the camps the same as they were in the previous games...but we still have Lower camp,forest camp and Blackwood tough hehe