These questions make me think using science for some reason so here we go. I believe that outfits don't and do at the same time because someone who wears athletic/sportswear is likely to have more physical strength then someone who doesn't but that isn't always true. I believe it all goes down to the limbs. It seems exposing more arms and legs in feminine world is used to attract boys in High School plus it's just a trend. Another thing is when it comes to the top, A non athletic top gives a much more different view than an athletic top no matter how much arm is exposed. So I believe it boils down to how many boys are attracted and how many want to take advantage and pull off some smartalec move.