Why the bleep haven't we solved robocalls yet?

Robocalls are a massive annoyance. Every day, unsolicited calls and voice mails and text messages for fake car warranties and lawsuits and spam links get delivered to people everywhere, and it feels like there's basically nothing we can do about it. What's actually happening here? Why did robocalling start in the first place? And is anyone working on the problem? Dr. Brian Stuart, Associate Teaching Professor of Computer Science at Drexel University joins KYW Newsradio In Depth to talk about why robocalls are so pervasive and why they're probably not going anywhere anytime soon.