Re: Potentially stupid question...
Genes. Your genes predispose you to a very specific fat and muscle deposition pattern. They predispose you to a specific tendon to muscle body length ratio. They predispose you to a specific skeletal structure.
These patterns, ratios, and structures will give you a "look" that sometimes isn't considered "ideal" by the zeitgeist of what's currently or evolutionarily considered "hot".
Aesthetic training programs like bodybuilding are intended to help fight these genetic propensities to some extent. But GPP programs like crossfit don't address this because you generally don't identify your aesthetic weaknesses and work on them. You train for performance.