For most players, a good lob serve can make them very anxious indeed. I once asked him to serve it to me, and I had a lot of trouble returning it. At his age, a good lob serve can win a match, but against younger opponents, it can still be incredibly effective. When outfielders track a pop-up, they must calculate both horizontal and vertical movement of the ball. When a ball is thrown to a first basemen, however, he has only to calculate horizontal movement.
Outfielders also have to deal with the wind and the sun.
The lights and the walls are similar impediments to the wind and the sun in that they can both force the receiver to make yet another calculation. The more calculations you force upon the receiver, the better the odds you will get a weak return. Ideally, the serve hits high on the front wall a bit past center. The hammer serve is a straight hard serve. Or if the ball goes to the backwall, the receiver may be forced to hit the ball at an awkward angle.