I think it all depends on your point of view, now let's look at the regular rules you pointed out:
Disagreement on rewards, this one is dumb, no one can know what I think is a good post, suppose a whale thinks anything x posts is ok, that's his prerogative, and I know no one down votes anything a real whale up votes for fear of a reprisal, so again this is dumb, it's like bullying you flag if the one who up voted isn't too big or you know you will get screwed.
Fraud or plagiarism everyone plagiarizes, even if it is just an idea and by putting a link to the source you are not legalizing anything, you don't have the author's approval so you would have to flag about 90% of posts.
Hate speech or internet trolling, what is hate speech? It is somebody's idea, this is a free speech platform so even these assholes with the hate speech have a right to post if you don't like what they say let them know it with a very detailed comment.
Intentional miscategorized content or Spam, How do you know it's intentional? As for spam, isn't it easier to ignore it?
And you talk about the people who use vote for vote etc. comments, and say nothing about people with big SP just commenting a post so they can't up vote themselves, is this not even worse?
So to me flagging is a big waste of time and anyone doing it is just someone with a too high opinion of himself or is somehow like the guy who can't stop from criticizing everything. To me, if you don't like something, comment on it, or just mute the guy, that way you are out of that circle. By the way I have never flagged anyone.