Volumes could be written, and have been surrounding the mandate to LOOK, LOOK, LOOK... Those who know will understand.
EC
You're so right about it's importance.
Tell a guy that's been playing for over thirty years to look at his hand, even in a Basic Motion, after impact. Tell him to look at his hand about 37,563 more times, then he MIGHT look at it. You can't get his attention away from watching the ball. Or, you could take my approach. Tell him, "if you don't watch your hand instead of the ball this time, I'm going to hit you in the head with this baseball bat."