cheese said:
Coaches get on officials because it works. You get the next call if you can do it within reason. You'll never convince me otherwise.
Parents, I'm less sure. I think they like to show off that they know rules.
Oh it can definitely help coaches if they do it properly. Refs usually know when they've made a mistake and a coach pointing it out properly will get them to work harder not to screw that same team again. Lazy refs will give a makeup call. ##### refs will punish the coach for pointing it out. I've been accused of both, but I've never honestly tried to give a team a makeup call or punish a team. Sometimes a play will allow for a call to settle down things. Sometimes a play will allow for things to escalate. I do my best to call what is in front of me, but there are times when we get together and say, "lets not miss any fouls on this end".
The three biggest things that coaches complain about that will get a response are
illegal screens, 3-seconds in the lane and off ball fouls on the defense. Those are things that are easiest to miss by an official. On ball fouls and travelling are rarely missed because you should always have eyes on the ballcarrier.