Dunno about this. At one time, prior to the internet and social media, I think that might have been the case. That was the era of Pete Franklin bragging about talking to more sports fans than anyone some 40 years ago.
Now, it's more entertainment, expert opinion, interviews, story telling, etc.
Callers are now viewed as "amateur hour." And in an era when you can put your opinion out there online instantly for prosperity, turning the show over whoever is still waiting on hold to speak and give his two cents that will fade in to the airwaves is probably not your strongest option to keep an audience.