If the defect (hole) in the part is small enough or the path length for the leak is long enough, it will be almost impossible for the fluids to flow through the hole (leak). The fluid properties that affect flow are pressure, temperature, and viscosity.
Though the answer seems to be correct, but when taken from that perspective, one will not keep focused on the real reason. The main reason why we shoe horses is for work, which then determines the style and the type of shoeing for the individual working horse. Various types of historical horseshoes.
When a horse does not wear horseshoes. Bearing rein, overcheck or checkrein. A strap running from a horse's back, over the head, to a bit, to prevent the horse from lowering its head beyond a fixed point. Used with harnessed horses. A riding aid where the rein is applied to the horse's neck on the side towards the turn. Opposite of a neck rein.