Once upon a time I used a flag against low value content (a single youtube link without commentary) and tried to use the flag to teach. When I watched this guy turn into a free speech warrior, and acuse me of being a bitter troll for abusing his right to share youtube links, that really started making me think about the flag narrative. I didn't teach that guy anything except that (at that time) steemit was uncomfortable because people flag.

Flags (downvotes) are not to teach people a lesson, as someone who has been downvoting well before it was cool and free, very rarely is it accepted well.

Downvotes are about putting the rewards where you believe they should be based on your stake.

While scamming and plagiarism are ideal cases for downvotes, you also have spam like churchofgod does by replying to almost everyone, you have people posting a image off the web and making more than our best authors. All these situations are good uses for downvotes. By removing rewards from users who are not putting any effort in you can ensure the ones that are putting efforts in will get a larger portion of the reward pool.