Trail riding is a valuable place to get your horse used to all kinds of distractions. For me, this is a great opportunity to prepare my horses for the busy show ring atmosphere.
But I understand WadiDraa410s trainers. Trail riding is also a place where a rider sometimes lets his horse goof around. Expecting intense focus on the rider during the entire length of the trail ride is kinda counterproductive. But that is what show horses are trained to do. So most trainers would rather not trail ride.