It's part of the whole tech self-important "Always be hustling" schtick. The same people who want an abstract at the beginning of every article that isn't written in inverted pyramid style.

That said, I've never liked talk radio (or even radio in general) very much. And am certainly not a fan of meandering chit-chat style podcasts. A lot of podcasts could also probably stand to be shorter as could many presentations. But even a simple 20-30 minute interview conveys information and nuance in a way that a transcript or article doesn't necessarily.

ADDED: There are of course also produced shows that are more than just the words spoken just as a film is more than a paragraph synopsis of the plot.