Horses with good conformation and structural sound hooves may do just fine all their life without shoes. Just being trimmed as needed. On the other hand, horses with less than ideal conformation, weak hoof structure or an involvement in equine sports will perhaps need to be shod.
Wild horses have though and resilient feet with strong hoofs because those who did not have that died a long time ago. Only the strong survive in the wild. Because they have to walk around in all kind of terrain and long ways to find food and water they have to have good hooves.
Domestic horses are bred for performance with little or non regards to their hoof health. The result of that is that many competition horses have week feet and horrible hoof quality. Many horses I have seen have so poor quality that the farrier have problem to make the shoe stay on the hoof, and every time the poor horse looses a shoe, more and more of the hoof wall fall of with it. And they cannot walk a meter without shoes, they get completely lame.
Many researcher confirm that horseshoes can do more harm than good, because it restricts the flexion of the hoof, which in time can lead to joint problems, cracked hoofs and other issues.
Horses with poor hooves have to have shoes or they cannot walk. But the shoe makes them needing the shoe, because the hoof like our foot get stronger when it can walk barefoot. But when the horse have started to use shoe it will take a long time for him to get strong enough to walk without pain if ever. So it is a bad circle and you cannot get out of it if you want to use the horse for something more than a lawn mower.
My own horses have always stayed barefoot except Luna who was shod last winter. That was because we had so much ice and I was scared she would slip and break a leg without shoes and studs on. But she have very good hoof quality and both her parents are barefoot competition horses. And after only three months with shoes we could really see that her movements got a lot better when the shoes came off.
Many people use boots for their horses, and they are very happy with it. They are connected with Velcro around the hoof and give the whole hoof a protection when they are out hacking. It is not made to be used for too long and they may fall of.