When regular breeds of dogs get into a little fight, one of the dogs often will grab the other dog by the ear and hold him - this ends the dog fight.
Most dogs inherit a set of canine social behaviors, sometimes referred to as "doggie etiquette". This includes things like "If another dog lays belly up - then the aggressor is not permitted to attack - because the other dog has already surrendered.
Individual dogs in fighting breeds, may or may not have inherited the "do not attack belly up dogs" inhibition - many men who want a rock hard dog that never gives up - they want a dog that goes down fighting, never gives up - but it is in dogs to surrender when they can't win, aren't on their home turf, or would just rather not fight.
Other fighting dogs might inherit the knowledge on how to surrender by going belly up - but have deleted instincts about inhibiting themselves from attacking a surrendered dog. This means the dog that doesn't want to fight can get killed easily when he surrenders.
It is sad, and it is sick to breed dogs this way.
One of the ways that an aggressive dog can stop a fight on a smaller dog, is to grab his ear and hold on - this ear hold doesn't always pierce the ear, the grabbed dog calms down and then is released.
But when a dog has his ears cut off, the other dog can not grab him by the ear. A dog without ears can't give up when caught by the ear, because he has no ears.
In dogs who still have the social codes and inhibitions that most dogs all use to have, fights between non-fighting breeds were more likely to be squabbles, that ended when one dog got hold of the other's ear, or one dog went belly up.
We have different dogs in our culture now - it is not possible to not have different dogs. Dogs only live about 7 to 16 years, and new puppies can be born to a pair of dogs only one year old. What dogs are, is a continual shift, a species always in the flux of change - a species that is always whatever we have been choosing them to be.
If we choose harder dogs for breeding stock - then our society has harder dogs. If we choose friendlier dogs as breeding stock, then that is what we will have in the years ahead.
Cutting dogs ears off, interferes with social clues, and the abilities of dogs to surrender, or to accept surrender. It is not nice. And if you buy from someone who crops their dog;s ears - then you are not my kind of person.