Hahaha good question. The original idea for the design was that this would be a base armor for a soldier to wear. Other parts could be added in to adapt to different combat situations. One of the armor setups basically made the character look huge, but didn't want to put a new piece over every part, so I made the thighs larger so that it would fit the design for the heavy armor part.
In the end the idea of adding armor on top of the base armor was scrapped, and the decision was to just model the thigh part smaller than the original concept.