A helmet is designed to provide protection to the top, back, and sides of your head as well as some of the forehead. A helmet is used typically when doing some sort of action that required protection; like riding a motorbike, or working in construction.
if you were to put the helmet over the eyes or ears you would take away one of the main reasons some has the helmet on for anyways. How would you work in construction if you can't hear when your being called or seeing where the blueprint tells you to place the steel beams. Or how would you see where you're driving or when someone is honking at you if the motorbike helmet is covering your eyes and ears.
Helmets are for providing protection, not disabling your senses.
