Why don't more teams do this?
Midway through the 2nd quarter of the FIU and Arkansas State game the announcers pointed out some pre snap activity on the offensive line that made us think...why aren't more teams doing that?
While in shotgun, the center would have his head up, scanning the defense, and the left guard would take a look back between his knees, and make sure the quarterback was ready. This gives the center the time to evaluate the defensive front, and make the necessary calls. Once the quarterback gave a signal that he was ready, the guard would tap the center's leg, giving him the green light to snap the ball.
After digging around a little we found that this technique has been used by the Indianapolis Colts as well. Notice the left guard in both pictures.