NMH uses the overworld less as a gameplay feature, but instead like a thematic foil. The setting is this desolate, dry, almost southwest/coast/something town that is mostly typical, bland, un-interesting, sun-baked and all-that, and its real purpose in the game is to contrast the vivid fantasies of the levels, characters, and circumstances. Sure the overworld serves as a hub, as a fetch quest, as a setting, but it also serves as something that's placed directly contrasting the rest of the game, as if to brighten the rest of the game by comparison.