If our offense sustains long, time draining drives, it limits the time the opposing offense has to score and essentially shrinks the game so that less points can be scored. Consequently, if your offense plays really well by sustaining such drives, a team can limit an opponent's points without the defense playing any better than another team.

Indeed, our defense could possibly play worse than some defenses who give up more points to the same team simply because the offenses on the respective teams have the ball less long.