It’s a common elemental theme we see across stories, fantasies, etc. It seems like it is an element that should be part of that pantheon but maybe there is a scientific explanation of why it isn’t? Or is it simply, they did not have enough understanding of it at the time those 4 were suggested.
I mean, what is “Aether” in a historical/classical context? Would that fit?
Edit: I guess not. Aether seems to be more like…‘dark matter’ or ‘gravity’ than electricity.