YouTube, just for one example, and according to one source, has 720,000 hours of video uploaded to it each and every day. To have someone at minimum wage watching each and every hour of that video for moderation would cost on the order of $3.4 billion dollars a year.
Requiring the same for smaller networks just moves the costs of moderation onto smaller providers less likely to be able to afford the costs.
Especially as smaller networks mean smaller audiences, which in turn reduces their ability to attract advertisers.