Why do horses need dentistry when wild horses don't?

Firstly who is to say that wild horses don’t need dentistry, it isn’t available to them and so they must either tolerate discomfort or become weak as a result of poor nutrition and die.  Studies have shown that horses eat for up to 18 hours in the wild, domesticated horses may only eat for a fraction of this time from haynets and other artificial sources, this reduced masticatory time means less wear on the teeth allowing greater overgrowth.  Finally the type of food fed to horses in domestic situations differs greatly from wild horses which eat high roughage and coarse diets compared to their pampered relations on soft meadow paddocks and selected grass forages.