Before he came on the scene carvings of the movers and shakers of the ancient western world were fashioned thus:
Neck, head, shoulders,etc., everything straight as a...well, straight as a statue.
But Alexander the Great was slightly deaf in one ear. He always tilted his head a bit so he could hear better. And he was sculpted that way:
As a result of this statues and busts began to show movement. At first it was out of respect to Alexander, but soon b/c people simply preferred them that way.
And that's fair dinkum.