[MrSeven]

Pitchers want used/scuffed/dirty baseballs. The scuffs on the baseball make controlling various breaking balls easier.

I think reusing a baseball that went in play is a clever way around the MLB rule that the baseball is supposed to be free of any foreign substance (including dirt). If a ball gets scuffed or dirty per the rules it needs to be replaced.

If the baseball never goes close to home plate and the umpire, the pitcher is likely going to be able to get away with using that baseball for one more pitch.