the hitters are so good that a pitcher cannot throw as many strikes as he would like if he plays division II ball or higher. Unless the pitcher is a freak like maddux or tewks. by the way, herzog didn't like tewks and delayed his call-up because he threw too slow (83 fastball). one of the only times herzog admitted a mistake.
a pitcher cannot throw the ball in the center of the plate if he makes any team past high school without getting hammered. most managers hate walks, but they also hate losing by double-digits and, for a pitcher, it would be a very short career. a pitcher also has to have movement on the ball. velocity and movement will perhaps cause a hitter to hit the ball 1/4 of an inch from the sweet spot, which is the difference between a pop-up and a crusher. a one inch difference is a miss. not much room for error on either side.
i'm sure you all realize how great these guys are. most all-state high school players and all-american college players do not even make the major leagues...and they were great ballplayers.