Let us do some math. There are slightly under 7.8 million questions on Stack Overflow, with only 17 moderators. Out of those questions, 347,109 of them are [at the time of posting] closed or on hold. If a moderator would handle each of these flags and close all of those questions, they wouldn't be doing anything productive. Moderators should only work on things that require their special tools to do.
Most people think that this answer should be deleted:
You don't need a resistor for a LED. A paragraph of explanation...
Of course, that isn't true. However, incorrect answers do not get deleted. They get downvoted, edited, and commented on. If you flag an answer like that, then it should be declined as not needing moderator intervention because you can downvote it/comment/edit it.
The only time an answer should be deleted:
- Low quality answers (not understandable, link only, etc.)
- If the owner deletes it themselves
However, incorrect answers are not deleted. If you flagged one of those, then the reason above is most likely the reason they got declined.
Edit: this post explains this problem with stuff that doesn't need moderator intervention.