Here's an excerpt that gives a scientific view on how excess spin reduces overall distance:

"Spin rates of 800 and 900 radians per second produce the furthest range. With the same initial conditions, a spin rate of 1000 radians per second is too fast of an angular velocity."

From the preceding portions of the paper this basically means the Magnus Effect (boundary layer around the ball pushing it upward) is greater than gravity and causes the ball to balloon. This prevents the shot from achieving its optimal distance.