Wild horses and equine critters such as zebra are not shod and they seem to do alright.
In the past, when working horses were used to pull coaches and dreys and the like on hard roads and pit ponies went down mines, then I can see that putting shoes on horses was must have had merit, in preventing the hooves wearing down and causing damage to the feet.
But now, horses seem to be mostly used for sport and mostly on grass.
So really, I suppose the question should be, why are horses still shod?
A few thoughts from a horse owner (but by no means a shoeing expert):
-In domesticating horses, humans have selected for the traits they most desired: speed, size or strength, for instance. For the most part “hoof strength” was never a bred-for characteristic.
-Some breeds of horses have stronger feet, on average, than others. Thoroughbreds are notorious for having weak hoof walls, for example. I have an Appaloosa horse and her feet are strong enough, that, if I was only to do light work or trail riding, she would not need shoes. Since I do jumping, this puts extra stress on her hooves, so she wears shoes in the competition season.
-Some shoeing is theapeutic and slows down degenerative conditions of the hoof and leg.
-Shoeing allows screw in “studs” (cleats basically) to be applied to the shoes for extra grip in soft footing. You can also put rubber between the shoe and hoof for cushion on hard footing.
-Most horses that are routinely shod benefit from going unshod for part of the year (typically the winter). This allows the hoof to spread and become a wider bearing surface.
-Even horses that are not shod need regular trims to keep the hoof growing level.
Wild horses and zebras seem to do fine without shoes, but the fact is if one has weaker hooves, it will more than likely die. So the stronger-hooved animals live and breed, the weaker-hooved animals die out before they can breed.
So, in the wild, what keeps a horse’s hooves level? Just regular wear? Do wild hooved animals display any sort of care behavior for their hooves (ie. scraping them on rocks or something)?
In the wild, horses and asses run across a wide variety of terrain, wearing the hooves. Domesticated horses spend a lot of time either standing on sawdust or straw with a sand base or in a grassy paddock. (This is especially true during the winter months when they may not be worked as often.)
In addition to the points that Hello Again made, recall that nearly all domesticated horses carry burdens (either riders or pulling loads) that wild horses never do, so there is additional pressure and, hence, wear on their feet.