Because advertisers don't actually want responsibility. They want to show their ads to as many people as effectively as possible. Advertisers go along with cont

Because advertisers don't actually want responsibility. They want to show their ads to as many people as effectively as possible. Advertisers go along with controversies to not get demonized by the media and activists for "supporting the evil people" and to score bonus points by doing what the media wants (so that the media talks about them). If you give this responsibility directly to advertisers then the advertisers are responsible for every single misplaced ad. They have no scapegoat if somebody comes knocking and asks why they support Mr Very Evil by giving them money.