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

@Gamer_34567544 No they don't compare, my favourite "worlds" will always be Moonlight Falls and Roaring Heights. When my sims were there I never felt the need to travel. San Myshuno makes me angry to this day. It is not a city, it's a collection of tiny areas with painted in backdrop.
That's what I meant by after spending a considerable sum. Eventually you end up with an area you could call a world.