Quote - I'm not sure what causes it either, it could be simply because they might wear long sleeve's with shorts or skirts (I see alot of people wear that type of style nowadays, lol). Or it could be the lighting, most professional photo studio's have those tall lamps and some are even extendable, but it's mostly pointed towards their upper torso/face...

During the last years i have done a lot of photo shootings of people in the studio. It is hard to get an even lit shot across the whole body. Even with a softbox big enough, the distribution of light might not be uniform enough.