I think it's a lack of preparation, both mentally and physically, a lack of desire, and a lack of focus when guys don't get bunts down.
Nobody expects players to consistently beat the shift. But if you can't go the other way then f*** you, that's not my problem. Have fun hitting into the shift your entire career.
You don't think big league managers cringe when guys make fundamental mistakes? If Kevin Cash wants you to get the bunt down, you better get the bunt down. If Terry Francona puts on a hit and run, you better put that ball in play, and preferably to the right side.
Wouldn't baseball be fun if we just played it on a computer and simulated all the games?! Now THAT's a sport