“Tiring out your opponent”
Truly, hitting a lot of overheads can wear a player down. So, if you figure that you’re in for a long, closely-fought match, you can tire your opponent by sending up lob after lob. That will force him to chase down the ball and hit overheads. Even if he recognizes your ploy and returns your lobs with ground strokes, he will still get weary. That’s because a ball that drops as steeply as a lob has no pace or forward momentum on it and has to be hit hard for an effective return. So you can use your lob to tire your opponent even when he or she’s playing most of the points from the baseline.