It's Good to Know What You're Getting Into
What's the first thing you do when you pick up a book? You heft it, you flip through the pages, read a page or two. You get a sense of the nature of the content and the scale of the commitment you are making by starting to read that book. If you're looking for a brief diversion and you pick up War and Peace, you immediately put it down because it fails your basic requirements. With printed media, scale is easy to understand: How thick is the book?
It's less clear cut in temporal media. With audio, you need to overtly tell your audience what scale of listening commitment they're getting into. You must tell them how long the show is. You must tell them the nature of the programming. At the very least you must tell them the title of the show. If you fail to do this BEFORE they start to listen, you risk making them feel trapped, alienating them, and losing them forever.