This is NOT in defense of the lower quality dog foods, nor is it an attack on successful long time show breeders....
Many of the most successful show breeders have been in the business 30 - 40+ years -- long before what we call "quality dog food existed". Purina WAS the big name in dog food and was accepted as the best
. So we have show breeders with kennels that have been spitting out champions right and left using the products that worked for them. When you have a kennel full of champions eating Purnia Pro Plan, it might be hard to convince them to change what they have proven works.
It takes a LLLLOOOONNNNGGGG time to grow a show coat so I'm sure that the "old school" pros hesitate to change what they have found through trial and error works for them.