Maybe, because the pitcher is throwing a change up when the batter has three balls in their count?
If the pitcher has thrown 3 straight balls the CU would be ill advised. I throw the CU for a strike early in the count even on a first pitch. Especially when I have had the 3rd base coach berate the batter screaming "WE DON'T SWING AT CHANGE UPS!!!". I have a young lady with a phenomenal CU who also bumps 60mph on her peel drop. On aggressive teams I will throw 2 or even 3 CU inside which usually get jacked foul into the adjacent field. Now at 0 - 2 we have established the off speed and our options are wide open, and a good time for yet another CU low and away.