They don't need to just give great cuts, they need to show they're well rounded in dealing with dogs in general, which is why they have tests like grooming uncooperative/aggressive dogs, puppies, specific breeds etc. They have a professional groomer to judge the cuts, a veterinary to judge how they handled the dog in ways appropriate for their health/breed, a guest judge tailored for each challenge (Publisher of magazines they are competing to be in, a trainer for difficult dog episodes, etc) and considering the fact it IS a reality show, a judge to be a jerk. It makes good TV.