It's because the relevant regulatory apparatus has been captured by the to-be-regulated industry in the USA. There's no technological gap that prevents us from dropping a smart bomb on telemarketers within minutes of their first spam call. We just don't care.
I got a call from someone who told me I had a virus and had to install some software so they could fix it. I told him he should find a new job instead of trying to steal other people's money. He repeated his script. I repeated mine. And after the third time he went off script and asked me, "can you tell me where I can find a better job?"
So there you go. Money making good people do bad things again.
Are you sure about that? In 2012 the FTC had a robocall summit with a variety of speakers. I watched the live feed and it seemed like they were quite sincere about tracking people down. It was just a hard problem given the rise of things like VOIP.