Why do quarterbacks always stomp their foot before the snap?

it is usually a signal that he about to have the ball snapped to him.

if you watch the nfl and see sometimes when they do that but nothing happens they'll repeat it more exaggeratedly, depicting that someone didn't notice that and they should've.

Edit by smorin1487: if a quarterback is in shotgun formation, normally the Center is looking between his legs to get a perfect idea of where to hike the ball. The QB must life his leg to indicate that a player is allowed to go in motion... in this case the Center will be allowed to lift his head up to look at the defense, and then he can hike the ball.