I can give you many reasons why a Presa must have his ears cropped, from health, to conformation, till function.
Of course first of all they do look better, but It’s not just about the look, because is a breed with dominant specimens, active dogs with high energy and love the fights, ears are the first who fall in altercations. And is well known that they are highly vascularized and from here could start a very „nice” bleeding.
Also a very important role is the ventilation of the ear, which is better done with the ears cropped.
Owners who have a single dog can avoid conflicts between their dog and others, but breeders who have more dogs and especially puppies, when they play toghether, some of them can hurt easily.
Not to count that their play, watched from outside is pretty brutal and they always will have scratches. So, this is a simple and easy way to prevent injuries and infections.