I believe they are inclined to allow themselves to be domesticated. Not all animals are prone to domestication. For example you can't get a zebra to be tamed. And of course horses are designed for riding: their backs and size allow for it. read more
Horses are herd animals, so unless the horse is the leader of the herd, the horse that we separate from his herd is looking for a new leader, and a person is an acceptable leader to him if the person handles that situation right. read more
Unfortunately, many horse owners keep and ride horses only to serve their egos. "Look at me, I am riding a beautiful horse! I can control this big powerful animal and win ribbons for riding it!" Horses that live a life at a riding stable do not have it great for sure. Many stables do not care well for their horses. read more