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

I guess it kinda simplifies it because if it was towns then it would be like
''no this is not a town this is a village no this isn't a town this is a city'' and so forth
guess they are more of ''new areas'' but that doesn't quite have same ring to it as ''new world''

also neighborhood would do but then that has problem with the smaller areas now being called neighborhoods