Is there any purpose for camping on a location in the kingdom map?

Not sure if it is just etiquette, but generally armies camped out don’t get hit. They bare no resources, and pose an unnecessary risk to attack. So use this option to keep your valuable armies from loss if your base is attacked overnight. Keep the camps a distance away to be sure.

You can use a camp to keep a spot, for example a place where you want to teleport to later. I use it to keep a place for the next KVK or when I go hunting to keep my spot for my return