Why are they called "worlds", and not "towns"?

TS 2 calls them neighborhoods, accurate in terms of your playable area, though I've always thought of village within gameplay as the overall map sub-divides easily into neighborhoods, at least mentally. The TS 4 versions might get away with being called towns in most cases, but no way are any of them 'worlds'. The whole game save, maybe, but not the units we play in.