Why doesn't Yi have energy as a resource?

He's obviously better off without it, but you could probably say that about alot of energy based champions. The main reason why i brought this up in the first place is because I've noticed over the years that the "ninja-like" champions are Energy users. Personally I can't really call him a ninja, but at the same time he does not look like much of a swordsman either. The logic probably isnt gold standard.