I started shadow swinging to shorten my take back habit. I was taking it back far in a mindset of hitting hard on contact. I had ups and down doing the said take back and started loosing focus on ball at tournament play.
Now, with a shorten swing I had developed the correct and long follow through -- complete to the fore/around and above shoulder. I always hit the ball on sweet spot which is nice to the grip and arm, but it will be weak without followthrough.
Shadow swinging helps me remember as tp when to stop take back early.