Originally Posted by Perry the Platypus
We look it akin to a catcher calling pitches. The pitcher (or server) can always shake off the call.
Maybe 30% of the time, it doesn't matter, but if you're facing a guy who has a tendency, I want to know where that ball is going with some certainty.
The other option is to talk between points, and ask them where they want to serve. We do that on more critical points.