Comment by Bartweiss

I'm surprised at how many other responses here are saying "because the police don't have the resources to investigate" and similar.

This reply gets to the more fundamental point: companies are doing a different thing than police investigations or even civil suits over harassment. They can't undo the harassment, they can't punish the harasser (beyond termination with cause), or force the harasser to compensate their victim.

Rather, the goal is to create a workplace where employees are not harassed. This is good for both legal reasons (hostile work environment suits) and obvious moral (harassment is bad) and practical (people will quit) reasons.

If a coworker mocked or punched me every day at work, it might or might not produce a complaint to the police or a civil suit against the coworker. But it would certainly be something that made my employment untenable and a reasonable employer would react to that. People are in general not demanding that employers act in place of the police, they're demanding that they act to stop sex-related hostility at least as thoroughly as they would act against other hostility. It's the purview of the company because it's a completely different task than what courts or police would do.