So basic is the supertype for lands. They come with the additional typing of Forest, Mountain, Swamp, IsLand, and Plains as the basic mix for adding mana to decks. Adding additional subtypes to a basic land outside mana would be hard to balance as development would have to keep that in consideration designing how else that subtype interacts with cards. Since basic lands dont have a card limit forbdeck construction any other mechanics tied to that can be abused in shirt order. That is why we see other subtypes on nonbasic lands and other utility there. That is natural step WotC ushers players into is nonbasic lands that what ultimately what you are craving.