Why does a person need eyebrows?

The human body is an integral system that needs absolutely every part of the body and has nothing superfluous. But if we are perfectly aware of what we need legs, arms, eyes, ears and other organs for, then in the case of eyebrows it is not entirely clear why we need them.
From a biological point of view, eyebrows represent the natural protection of the eyes from sweat dripping from the forehead. Without them, sweat would get directly into the eyes, which would be irritating and cause temporary visual impairment.