The real problem is partially included in the question. Affordability is a major concern to most horse owners and farriers alike.
Farriers do not impose steel horseshoes on the client however it is the most affordable and durable material currently in use.
A good farrier will have a range of alternatives at his disposal. Aluminium, titanium, glue on shoes, plastic shoes as well as the range of different products designed to replace missing hoof wall.
All these products can be substituted for steel and in some cases are more beneficial for the horse, however they all come with a higher dollar value and usually they require your farrier to prove he has greater skills than the bloke who just hammers steel shoes on to poorly prepared hooves.
Most farriers would agree that nailing steel shoes onto a horse hoof is not ideal.
Interestingly, enough the Merovingians of the 7th century are thought to be the inventors of the nailed on shoe. They used iron of exceptional purity that was both malleable and tough.
Apparently it would conform to the natural movement of the hoof while also protecting it from excessive wear. Unfortunately this metal working technique was lost and later replaced with the advent of high-carbon iron, a much more durable and robust product. The farriers of the time identified the problems (too thick and heavy) associated with this product which was to become mild steel and they have been searching for a viable alternative ever since.