Why do horses have tails?
The function of the horsetail is to ward off the flies. Before the manes come into action, the swinging motion of the tail keeps away all those insects.  Furthermore, the movement and position of the tail help in judging whether the horse is comfortable or scared in a specific environment.  Similar to the manes, the tail also requires utmost care. The hair of the horse is groomed to make the horse look attractive.