Also, I think most musicians (not 'entertainers') are a little bit introverted (shy, self-conscious) which is why they are better able to express themselves behind the protective barrier of an musical instrument. Just a guess, though.
chas
That's a darn good guess. I think you nailed it right on the head. Although I'm also an entertainer and go out on the floor to mingle during a performance, I'm never comfortable with the "body movement" part. I need to know the piano is right behind me so I can retreat to it if my clumsy moves don't come out right. But I CAN do the Charleston!