Why do we slap iron shoes on horses?

It protects the hooves from deterioration.
Horses do fine in the wild but in captivity, we put them to work in a big way.

wild horses’ feet are used to rough terrain, while domesticated horses are not because they are kept in stalls with hay and usually ridden on dirty or grass (i.e. soft surfaces). over time domesticated horses have genetically developed softer hooves.

it is possible to let them be barefoot (or “barehooved”) but that requires a lot more hoof trimming and care taking.

http://www.curlyfarm.com/articles/why_horse_shoes.htm

http://www.healthyhooves.co.uk/why_shoes.pdf

Horses hooves are their Achille’s heels, so to speak. From the time they were first domesticated, their owners realized they could be more productive with hoof coverings. The Romans rode them over paved roads that required protection against excessive wear and abrasions. Farmers used horses in marshy fields whose dampness could damage porous feet. And professional racing is too harsh. Imagine walking barefoot over stones or in muddy fields 10–12 hrs/day, let alone running a couple of miles daily in any weather-Ouch!

Hooves are really just really thick versions of fingernail material. Think of all the jive that can happen to fingernails, if they were walked on through pavement and rough terrain, imagine them splitting and how painful that can be. Hooves are sturdier than fingernails, of course, but they’re not made of iron. ;) Unless someone helps, that is.

My cousin is off to farrier college, I’ll ask her when she finishes her course

@laureth and a lot of weight to be carrying while walking on your toenails. For the most part early horses were a lot smaller.

Same reason why big dogs get hip dysplasia- we bred them to be bigger/stronger, and there are some unintended consequences.

“Are their feet not sturdy enough for roads of rock?”

No, their feet are not sturdy enough for roads of rock. Besides horses in the wild don’t live as long as horses that have been domesticated, and we like to “protect” our investment. A horse with a foot problem is a horse in great trouble.

Horses didn’t evolve to be able to go as hard as humans often push them, so their hooves wear away rather quickly without them, and if they grind down too much they can’t stand, and are often put down.

Eddie Izzard has a bit on this. See 1:30.

Horses have moral objections to leather shoes.