Such systems are either signed, and thus barely used, or anonymous and thus easily exploited.

Journalists that could speak with people at length and confirm the story by further research still weren't willing to publish based on anonymous sources. This is in part because anonymous accusations can be a great tool in a defamation campaign.

Furthermore, publishing anonymous claims without due-diligence discredits future anonymous claims. It might even back arguments like "Those sexual harassment claims always turn out to be smear campaigns".