its the law in many places. Here in australia ,even pet greyhounds must wear muzzles. They have a very high prey drive ,incredible eyesight,and even greater speed,so it really is safest thing for everyone. They may be the sweetest dogs ,but if they see a chihuahua,maltese or cat zooming about,its fair game! The same dog may well sleep with a cat at home,but when its at a distance ,moving fast,the greyhound just cant help itself!
I really like geryhounds and have had 3 ex-racers as pets.
From what I have heard about the muzzles, is just a protection for the other dogs. They get excited while racing and having the muzzle on protects everyone. I could be wrong but that is what I've heard.
"There is no psychiatrist in the world like a puppy licking your face."