Ok.... Teams line up at the line of scrimmage. Offense barks out a few preset calls....sees what the defensive set is, the all the offense stops, looks over to the sideline, and the OC makes the play call depending on what he sees in the defensive set.

Obviously, the OC makes a call to take advantage of the defensive alignment.

So...why doesn't the defense, line up in some base defense ...as soon as the offense looks over to the sideline for the play...as soon as the offense turns to the line...the defense totally shifts in some other set.

Do they do that already?