I watched a lot of games in the 2012 MLB season and the same questions kept popping in my head: Why is the hitting so poor league-wide? I came back with 2 constants: an all or nothing approach and terrible plate discipline. I followed the Chicago White Sox all season and was frustrated watching them trying to hit home runs no matter what the situation, and refusing to take pitchers deep in counts or take walks. Their manager, Robin Ventura, subtly complained on several occasions that the Sox hitters needed to try to manufacture runs and score in different ways other than homers. But they couldn't do it, and that was the biggest reason why they lost their division after being up 3 games with 2 weeks to go in the season. The opposing teams correctly surmised that if you stopped the Sox from hitting home runs you would have a great chance of winning.
Why couldn't the Sox make adjustments? Was it coaching? The coaches espoused the proper approach: hit the ball where it's pitched, take the ball up the middle and to the opposite field, swing at strikes and take balls, and make starting pitchers throw a lot of pitches to wear them down.
It was the fault of the players, who couldn't or wouldn't change, and continued to swing at pitches out of the strike zone while swinging for the fences. Same thing with the New York Yankees. They led baseball in homeruns, and homeruns consisted of more than 50% of their runs scored. But when it mattered in the playoffs, they couldn't score unless they hit homeruns. This is why the Detroit Tigers, who were then swept in the World Series because they had the same trouble versus the San Francisco Giants, swept the Yankees.
So how does this affect youth and high school hitters? They watch the homerun or nothing approach by their favorite pros and of course they are going to try to do the same thing. While coaches are teaching them the correct approach, in many instances the players will refer to what they saw the pro hitters do, which is counterproductive to the development of youth players.
My advice to coaches is to maintain the right course and to continue to teach the right approach. Ignore the pros until you become one!