Power
A talented and experienced farrier has a great deal of power among horse owners. Seriously, a farrier can make or break your horse (so to speak, of course). A master farrier with an excellent reputation may have a waiting list of owners who think they are the "farriest" farrier of them all.
Farriers, especially the more experienced ones, can spot a problem with a horse its owner may not have noticed and subsequently recommend treatment. In horse-owner circles, farriers have a great deal of influence.
If a famous horse has a problem and cannot race, lots of people may be affected (including the movers and shakers in Las Vegas). Normally, a farrier's recommendations about a horse only affects the family owned by the horse. And, yes, we wrote that correctly. Think about it in human terms. A little baby does whatever he or she wants. Sleeps, eats, plays, and more while mom and dad move mountains to keep baby happy. Who's really in charge? That's right, the baby.
Ultimately, a farrier's main concern is the overall health of a horse's feet. If necessary, farriers worth their salt will risk making an owner mad rather than risking the health of the horse.