The simple answer is that community moderation takes a human labor force, the cost of which is substantial and conflicts with the profit motive of the companies involved. There's just no financial incentive to clean things up beyond a threshold that would result in lawsuits or reputational damage. Because this kind of "toxic" behavior is becoming more normalized, and typically doesn't rise to a liability, you're not going to see most companies address it. This is why it has become customary for online gamers to have fucked your mother last night.