Why do pitchers walk other pitchers (in the National League) with some frequency?

Question

In asking this question, I am not referring to exceptional cases like Yovani Gallardo, Madison Bumgarner, or Jake Arrieta, who hit about as well as position players. But I am referring to "most" pitchers, whose batting averages are in the .100s, about half as high as average position players.

I read somewhere that there is a theoretical batting average below which it was right to always throw strikes because the chances of getting the person out was so high that it was worthwhile not to give him a chance to walk, and as a practical matter, there was a somewhat higher threshold below which it made sense to throw mostly strikes, thereby giving the batter a minimal chance to walk.

My best recollection is that the rule is that one should "never" walk a batter (incurring a sure loss) whose average was below .075 even if he all home runs, and that it made sense to never walk a batter with an average as high as .225 if he never made extra base hits.

Don't most National League pitchers fall beneath these thresholds as batters? (Or if I have stated them wrongly, the "corrected" ones?) So why do pitchers often throw enough balls to walk them, when they could get them out by throwing mostly strikes?

Put another way, why does practice differ from theory in this instance?

Answer 1

Pitchers don't try to walk anyone, most walks come from poor execution on the pitchers part/ bad calls by the umpire. Also, pitchers (while hitting) walk less frequently than positions players, indicating that the pitchers throwing are aware that the pitchers hitting can't hit.

Answer 2

"In theory, there is no difference between theory and practice. But, in practice, there is." -Jan L. A. van de Snepscheut (at least according to Wikiquote, although variations seem to predate this version)

The question seems to presuppose that a pitcher has absolute control over his pitches. Obviously, that's not true, or you'd never see a walk or hit batsmen with based loaded, a tie score, and the game being in the bottom of the ninth (or in extra innings); however - while rare in the Major Leagues - such things do happen, demonstrating that pitchers don't always execute their craft perfectly, which Frank Anderson's answer already addressed somewhat.

At a bit of a deeper level, I believe there are psychological aspects that can play into this when a pitcher comes up to bat. The pitcher on the mound may relax when his counterpart comes up to bat; in doing so he may lose some focus - enough that his ability to throw strikes is diminished. The flip side of this is that the pitcher who is pitching may get nervous due to thoughts like "This guy is a poor batter, so I must get him out." This sort of extra stress might be heightened if the batting team is threatening to score and the batter before the pitcher was intentionally walked to bring the batting team's pitcher to the plate.

There's also the possibility of walking the pitcher for strategic reasons. (While it might be the defensive team's intention to walk the opposing team's pitcher, they wouldn't issue an obvious intentional walk.) Pitching is probably the most tiring position in the game (if it is not, it is #2 to catching). Sometimes it seems that running the bases tires out a pitcher. Since pitchers usually become less effective when they are tired, a team might walk their opponent's pitcher to wear him out a little faster to either improve their chances of scoring off him, or to get him out of the game faster.