Certain pitches have a tendency to be hit differently. For example, with dropballs you can expect more grounders, with the rise more popups/flyballs. Location plays a part as well. An outside pitch to a righty will usually stay on the right side of the infield.
As a third basemen playing slowpitch I would always make sure i know what is being pitched, as a inside pitch would be coming fast.
Your infielders can get that extra jump if the pitch is in the location called.
The very first thing infielders, especially 3B with right hand batters and 1B with lefties, is whether the pitcher is throwing a changeup. You don't want 3B charging when the batter has plenty of time to pull the bat back and smack one down the 3B line.
The more a fielder understands about the game, the more knowing the pitch will help the fielder. Riseballs are more likely to get a flyball or popup; drop balls are more likely to get groundballs. If the pitch is a fastball, then, depending upon how fast the pitcher is, the ball might go to the right side or left side. Same with ball position.
But, every fielder should know if the pitcher is throwing the change.
I haven't seen it in softball but I've seen MLB games where the SS or 2B communicate the pitch by holding up signs behind their backs to the outfielders.