This is one part of the truth, but not all of it. The remaining minutes of the the hour long podcast evidently provide enough value to the listeners for them to keep tuning in, despite the annoyance of ads. As long as his output has value and he charges what the market will bear (in terms of ad time), he should do well.

The point is, it's not a net "waste" of people's time, it enriches their lives in some way.