Was told in the day that for road racing, the benefit of shaved legs was primarily to minimise dehydration fluid loss. The whole natural point of hair is warmth in cold, but helps cooling in heat. It provides much more surface area for sweat to evaporate from In the available airflow. The claim was that riding in essentially a 35-50 kmh breeze all day meant you still got the cooling airflow needed without sweating as much.
Also, it looked better. 🙂🦵