> Evolutionary speaking, it makes complete sense for animal to evolve steel-tipped horns: these steel parts hurt no one but their enemies.
Lightning might be an important consideration here. An animal's chances of getting zapped would go up significantly if they were waving around metallic horns in a storm.
Given that you're only talking about centimeters of metal at best, which in a thunderstorm could be covered in water anyway, and still need to interface to other tissues to achieve conductivity to the earth, then would the animal's chances of getting zapped go up significantly?
Lightning might be an important consideration here. An animal's chances of getting zapped would go up significantly if they were waving around metallic horns in a storm.