Why Do Baseball Pitchers Lean Over to Get Signs?

Question
Hello,
 Why is it that most (I know not all..) ML pitchers lean down when gettting signs?  Randy Johnson does almost a 90 degree lean, and most pitchers lean somewhat.  I don't get it, is it to see the signs better?  I cannot imagine that an extra 2-3 feet can help vision that much.

Tim

Answer
Actually vision is the number one reason.  Others do it as a form of intimidation on the mound.  A guy like Roger Clemens stands very upright, but has his glove in front of his face and stares at you with those asassin eyes.

Other than that, it is mostly just a habit.  The pitchers of today imitated the pitchers of their youth and have just continued the trend.