The following is a excerpt from the Unwritten Rules of Baseball*
Rule 69 (a).
When an opposing pitcher is down 3-0 in a count, the batter will take the next pitch, allowing the pitcher an opportunity to work their way back into the count
This has been a common practice in the game of baseball since forever. Pitchers will fall behind in a count, 3-0, then the hitter will give them the chance to just get a ball over the plate for a strike. After all, the hitter still has every chance to wallop a 3-1 pitch and if the pitcher happens to miss with their 3-0 offering, they get a free pass.
However, pitchers have taken advantage of this and have often just tossed a batting practice fastball right down the middle for the called strike in a 3-0 count.
According to Statcast, during the 2019 season, pitchers fell into a 3-0 count exactly 7,564 times. With their 3-0 pitch, the pitcher yielded a free pass to the hitter approximately 33% of the time. Meanwhile, pitchers would throw a 3-0 pitch in the ‘heart’ of the plate 35.3% of the time.
Of the 732,473 pitches that were thrown in 2019 in all other counts besides 3-0, only 24.8% of them came across the heart of the plate….