Telcos need to implement STIR/SHAKEN in a binding way and it needs to be fully integrated into iOS/Android's UI. Spammers call from spoofed numbers, even numbers of, say, local schools (or from other people in your business) - so, if you get a call from a school and you've got kids, would you pick up? A couple of years ago I got a text that was "sent" from my boss (he didn't send it), etc.. The numbers aren't random.