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.
Electricity is just wind and fire combined.
Or something… Like this isn’t entirely a joke. That’s how the classic elements worked. Other forces of nature were simply combinations of those four.
Modern science is essentially the same, we just recognize way more elements that make up everything else.