Yup, IDK abt any significant aerodynamic advantage, but there is definitely an advantage in preparing for road-rash. When you get it, you won't have to go through the pain of shaving in and around your ground meat to remove the hairs while cleaning and prepping for bandaging... so it may help quicker healing

At any serious level, there's plenty of psychology and self-motivation in winning competitions. So whether it actually helps them win, or makes them feel better about their efforts - don't knock it.