See the thing is that YouTube (and every other company whose business model is “serve ads next to user-generated content”) will let pretty much anything go through unless it is something that will generate huge fines, or will get advertisers to walk away. They are aggressively amoral corporations whose only motivation is profit, and they will promote anything that results in people seeing a lot of ads, regardless of whether what the ads are being placed next to is healthy for the viewers or for society at large.

Saying “hey big advertisers do you know your ads are showing up on this hideous thing” is one of the few ways available to try to get some sense of moral accountability to one of these platforms. Reporting individual pieces of content or individual users does nothing, if it’s drawing paid views there will be another person doing the same thing that the system will be quite happy to start promoting until they, too, get reported.