you also get much smoother lines.  with shorts under your tights i imagine there is a clear line around your thigh, which breaks up the beauty of the movement,  also, i am in a college ballet production right now, where they are very short of male dancers, (excluding the guest artists from the St. Petersburg ballet, only 2 of us take ballet,)  and many of the guys are just wearing their normal tighty whitey's under thier tights.  it looks AWFUL.  you see the lines around the back, and in the front, lets just say there is no concealment at all.  as well as protecting the jewels, a dancebelt gives you a nice amorphos lump that is much more flattering