> This is like wanting private phone calls, but also blaming phone companies for sex lines.

What are you on about? This is precisely the kind of situation where a best-effort can be done.

Though let us swap your example of "sex lines" for something legitimately harmful. Scamming callcenters.

Should they stop all scams? No, they can't. Inspecting phone call traffic to monitor for scams would be extremely invasive. Should they disconnect the firm they and everyone else knows are scammers? Yes.

Thus the point. When these companies don't make a best-effort, the government gets involved.

The only added complexity here is that the chat apps themselves can't do anything. But the big tech giants could stop making the problem infinitely worse, big platform holders who already monitor publicly-posted content could work to ensure their reports are actioned upon.