The reasons I would say:
Waistline is way to big for your height and weight
Conditioning is not good enough, primarly hamstrings. So the upper body and your legs don`t match
Rookies often take too much care about their weight and on competition day they are simply to heavy.
You have to learn that it doesn`t count how you feel, or how you look in clothes. If you`re ripped and 6-8 pounds lighter you`ll actually
look like you are heavier than that.