praia is obviously right to say that not all cockers suffer from ear problems, and a little wax in the outer ear is not a cause for concern. However, you cannot escape the fact that due to the anatomy of the cocker's ear canal, and the reduced ventilation due to the ear flap, cockers are more susceptible to ear problems than many other breeds and a lot of our dogs will suffer from one or more ear infections during their lifetime. If these become chronic it can be miserable for the dog. Many vets, mine included, recommend regular cleaning.
I'm definitely not one for overtreating dogs, and I have already said that I believe owners should adjust the cleaning frequency to suit the needs of their dog, but by the time the ears smell and the ear is oozing dark compounds it will already be infected. I believe that regular cleaning is a small price to pay to try to keep the ear healthy.