the massage and healing of injuries is the correct answer. It makes absolutely zero aero advantage.
Personally i prefer it, it feels so much better when riding as well generally and you look alot better than wearing lycra with hairy legs. Some people dont want to do it and others do, its personal preference. At the professional end of the sport is what pro's do so natural progression means semi-pro, amateurs do it and it filters down. Alot of people enjoy getting on board with it. All i would say is try it, if you dont like it then wait 8 weeks and nothing will be lost. You never know though, you may like the smooth feeling