It’s a horseback ride.
In professional horse racing, jockeys are often smaller in stature than other riders because it makes horseback riding more straightforward and balanced. Tall persons, especially those with long legs, must have their feet in the stirrups at all times; yet, their feet frequently go considerably lower than the mainframe of the horse.
Given that stirrups and feet are two of the most important methods in which riders connect with their horses, this can present a logistical challenge that discourages tall people from participating in the sport as a whole. There aren’t many horseback riders who are seven feet or taller on the trail. This is most likely the reason.