IMDB itself already includes podcasts. I think your question is really why you and others don't seem to know that. The Joe Rogan Experience, which as far as I understand is far and away the world's most popular podcast, has 4.5k total ratings. Gen V, which has existed for a month, already has 19k. Podcasts just aren't that popular. But it's nothing specific about the format. Largely informational, non-fiction content, even extremely high-quality, long-running classics, don't get much attention from critics and discussion groups. Nova has been running for nearly 50 years now and has 3k ratings on IMDB, even fewer than Joe Rogan.