Mankind is a harsh species.
I think it's do with the long term "protection" of those animals. How many animals end up in the pound?, how many people would take the time with a deaf dog?...it is a harsh reality sometimes someone has to make a judgement call for the welfare of the animals..long term. If those animals breed, you're only perpetuating the problem and contributing to the potential for many more animals being neglected, possibly abused and euthanized as an adult, or near adult animal.
Decisions like that are made every day, by breeders for many types of animals and farmers etc.
I got my dog neutered BECAUSE of her hip dysplacia...for the same reasons.