To your point, even if you are intend to run a hurry-up offense, there are times when it makes sense to SLOW TF DOWN.
Too many times our D would finally get off the field, either by a punt or score, then the offense would start at the 22 and run 3 plays that took only 0:50 seconds off the clock. This might consist of a caught pass and a running play, after which we would snap the ball with 20+ seconds on the play clock. Add in one incomplete pass and your 3-and-out not only rested the D for less than 5 minutes (3 minute commercial and 2 minutes of execution), but it took less than a minute off the clock, lengthening the game. This happened numerous times. An air-raid offense should only have the rare 3-and-out from their own 20. We usually had at least 2 per game. Often on the opening drive.