Podcasts aren't expensive to produce at a basic level, it's mostly just the hosts sitting around and chatting on skype for an hour every week or two. I'm only aware of one podcast I listen to that frequently asks for contributions, and that's mostly because the hosts have found they work best when they're physically co-present and have to fly one of the hosts out every month to record a bunch of shows all at once.
> I'm not too bothered with these, as compared with the type of adverts you'd find on commercial television or radio
Yeah, I agree. When the parent discussed adverts before I was thinking of the more commercial radio type. I think it's an effort to try to monetize podcast audiences, but at least for me I'm able to find more content than I can listen to, run by hosts that aren't all that interested in turning their hobby into a money making venture.
I'm not too bothered with these, as compared with the type of adverts you'd find on commercial television or radio, they're not that annoying and usually relevant to the podcast subject matter. If they started playing multiple irrelevant adverts back to back, with accompanying audio compression, then I'd be upset about it.