I've figured it out.

Women's nipples are friction-powered conductors that recharge their battery when stimulated. That's why they wear bra pads, because they rub the nipple all day so they can stay awake. It's also why their nipples are sensitive.

Men generate charge through sheer willpower so our nipples aren't as sensitive. But it does generate a shock to equilibrium when we're kicked in the balls.

Further updates will be recorded.