- the people asking questions just want a solution for their specific problem, which may or may not be useful to SO. This can include homework problems, RTFM problems, vague and unclear questions, etc.
- the people answering questions want interesting questions that stimulate them to keep using the site. SO really needs those people to feel happy answering questions, otherwise no one will visit the site! You need experts providing quality answers, who can find something interesting.
- the people visiting the site after-the-fact. Those people are (usually) just googling a problem they have, but aren't willing to commit to a question. They need both the questioners and the answerers to have done their jobs, otherwise either the questions are too poor a quality to be sure it's the same problem, or the answers are too poor quality to be of use to them.
To all those groups, effective SO moderation looks antagonistic, because they wouldn't go to the site if it had awful moderation - it would just be "that useless place where no one answers your questions and you keep getting the same question over and over".
You can use the chat site, message them directly (if their contact information is listed) or anything else you like to help someone with a useless/duplicate/beginner/help-vampire-ey question. You just aren't allowed to do it inside the reputation system to mine these kinds of answers for karma, and aren't allowed to do it inside the wiki system so you don't pollute the results of searches.
I've been frustrated when trying to contribute - you'll have two people helping each other and then some third party comes in and declares it not valuable, incorrectly says something is a duplicate, or starts deleting things for arbitrary reasons.
I just want the moderators to go away and leave us alone, it also makes me think stack overflow is successful in spite of this - not because of it.