It's combination of things:

1. Some people are just born with better control. Whether throwing a football, baseball, or shooting a basketball- some people are just born with that free flowing accuracy. I was one of these people. It was just always easy for me to throw strikes or put the ball where I wanted it. And that's a big, big plus when you only throw 81.

2. Some people develop it thru better mechanics and lots of hard work. Eventually they get to the point they can get the ball to where they want it fairly consistently. As was mentioned- some do it 18, some 20....and some at 26-27

3. Some people never find the consistency they need. They just cant do it on a consistent basis and that power arm just goes to waste unfortunately.

4. Some people develop it- but they arent mentally tough enough to do it when it matters. Their control is solid when pitching 5 runs ahead or 5 runs behind- but with the game on the line- they cant handle it. It's the same as the QB that struggles in crunch time or the guy on the basketball team you and everybody else knows doesnt need to take the shot when the game is tight or on the line.