North as up makes sense if you expect everyone to have a compass (or GPS unit) or travel by night using Polaris. East as up makes sense if you orient yourself each morning with the help of the rising sun. South as up makes sense if you are Australian and tired of being portrayed as at the bottom of the world (http://flourish.org/upsidedownmap/mcarthur-large.jpg).

West as up direction? Well, maybe you got your map from a contrary old eccentric. Those guys know where the best secret locations are.