Why do we do that?

[Clint]

Antoher good reason For calling fair/foul befoe catch/no catch would be R3 and hit deep to left on the foul line...R3 taggs up and scores...coach asks you if it was fair or foul this way he knows if the fielder should of caught it (if he lets it drop foul no run scores). But you payed no attention because you didn't think it mattered...uh oh now what?