Why can't singers (Particularly rap artists, if you even call that art) stand still while they perform?

[gummyroach]

Just a fun question to see what kind of answers are out there.

Ever notice that singers can never seem to stand still? They've always got to move their hands and arms up and down at some point during their performance.

I know "rap artists" is an oxy moron, (UH OH!) but have you ever seen one perform while standing perfectly still? Is it a requirement for performers to fling their arms around like they are having spasms of some sort?

Just wondering!