There are prep Coaches out there who do not seem to understand the first thing about the biology of weight control. This is unfortunate as many trainees will adhere to whatever is put in front of them out of a strange sense of loyalty, because someone looks the part, or even fear of not achieving optimal results. I will say for the record it is not difficult to starve someone in to contest shape, and make up for catabolism with anabolics and/or other pharmaceuticals. They may win a show, but they will certainly lose long term. The "win a battle, lose the war" analogy comes to mind.
The rituals of endless cardio are a waste of time, but to the extreme dieter it mentally and emotionally keeps them away from free time which would be otherwise occupied with food temptations, and also takes them further in to an apathetic state. This makes it easier to avoid acting on food compulsions at least till contest stresses are over, then the real damage begins