For the Corso it is the historical look of the breed.
They have always been a crop docked breed. Back in the day was for various reasons that no longer apply
such as hunting, guardian, what not.
Now it is the look of the breed. Ears change the expression of the dog, and unfortunately after so cropping for so long, breeders did not focus on correct ears so they are all over the place. People will tell you less ear infections and what not but I have had both cropped and natural and have never noticed a difference. If a dog is prone to ear infections they will get them.
When I see a nice, true to type Corso that is cropped it will stop me in my tracks. It is a majestic and noble looking dog, striking IMO. With ears I see a good looking dog, but not a Corso. I have a hard time seeing expression past the ears.
It does as well change the outcome in the ring. In North America you have a ring of cropped docked dogs and one with natural ears, the judge won't even look at the one with ears.