While many tennis swings are fundamentally described as lifting efforts, there's a potential problem with hitting ground stokes while using too much vertical drive. If the player's head moves upward too much while swinging, that can cause too many mis-hits.
As we swing at a point in space where we expect the ball to collide with our racquets, that contact zone is located relative to our point of view (the position of our heads). Move your head upward too much and that point of view also moves... but the ball still arrives in the same spot. So instead of catching the ball in the heart of the string bed, that altered point of view moves the swing upward and the ball catches the frame.
Easier in this case to hit a moving target (the ball) from a more stationary point of view.