The goal of any defense should be to get off the field as fast as possible and give the ball back to the offense. The best way to do that is to get a sack fumble or snag an interception, but with turnovers being a less sticky stat, forcing opposing offenses to go three and out is a good predictor of overall defensive success.
When you force the opposing offense to go three and out and punt the football, that gives the offense the ball back quickly while forcing the opposing defense back on the field, leading them to play more snaps and wear down over time.