For some people, muzzles evoke a sense of aggression to other people. Maybe, in your country: your dog breed must wear a muzzle as in the United Kingdom pit-bulls.
Why A Dog Would Wear A Muzzle?
Tendency To Be Aggressive
In some cases, the breeds have a history of being aggressive. Or, your dog might have a tendency and your vet/trainer would recommend your dog wears a muzzle.