The "beauty" of baseball's complexity

A few minutes ago, Alfredo Aceves was charged with pitching a ball to Miguel Cabrera despite not actually making a pitch.

Why?

Aceves touched his fingers to his mouth.

We see pitchers bring their fingers to their mouths all the time. They blow on their fingers to warm them up. They cough into their fists. They get moisture from the tongue in order to grip the ball better.

But apparently, the rule is that a pitcher cannot bring his fingers to his mouth while standing on the rubber. You have to step off to lick your fingers, cough, sneeze, or blow on your hand.

Why, MLB, why? What is the basis for this rule? What difference does it make if a guy licks his fingers on the rubber, or standing two inches behind it? How does this disadvantage the batter, the runner, or anyone else??

Naturally, you can do anything else with your hand while standing on the rubber. Want to adjust your hat? Fine. Want to wipe the sweat off your forehead? Fine...just don't touch your lip on the way down. Otherwise you'll get saddled with a ball you never threw.

This rule clearly has nothing to do with doctoring the baseball, because if that were the concern, the rule would prevent touching your mouth with your fingers at any time at any location. Instead, under the existing rule, you could step off, have something in your mouth, put it on your fingers, and then step back on the rubber and make a pitch. So because the current rule does not prevent doctoring the baseball, what is this rule designed to do, exactly?

I normally love the complexity of this game, but this is a stupid rule.