The other possibility is that the offense is reacting to what the defense is giving them. On a second-and-long, the defense might be anticipating a pass and res

The other possibility is that the offense is reacting to what the defense is giving them. On a second-and-long, the defense might be anticipating a pass and responding with pass-defense personnel (lighter edge rushers, nickel/dime personnel substituting for a heavier lineman). The offense might then chose a run or draw play since it would be easier to run against smaller defensive personal.