A batter is to be ready to enter the box. If he delays by not getting in the box or walks off after a pitch, a strike can be called. Part of the speed up rules is to keep the batters near the box. Another situation is if a batter ask for time but it is not granted and he walks out of the box, if the pitch is delivered it is a strike no matter if it is in the strike zone or not. I always try to keep the batters near the box, on very few occasions over the past years have I called a strike on the batter. This has been a rule since the 1990's .