Basically, radio hasn't changed over the years. Despite all the technical improvements, it still boils down to a man or a woman and a microphone, playing music, sharing stories, talking about issues -...
Songs used to be short, then they became longer, and now they're getting shorter. But otherwise, music is about a beat and a message. If the beat gets to the audience, and the message touches them, yo...
That something extra, I believe, is a certain humanity that comes from upbeat and positive human interest letters and success stories. Advertisers like to be associated with those qualities.