For all the attention D&D writers and players alike give to them, the Elements are remarkably ill-defined in terms of what they do for the world. Writers, DMs, and players come to the games with certain expectations about the elements, but they rarely write their expectations down and declare how the elements work, or even what each element means. Add that to the weird matching games done between elements and damage types, which aren't even played consistently, and nobody even has any idea what a "Water Monster" actually does. The end result is that the elements themselves end up a confusing mess.