I found this question on Quora and responded.

Any answer is going to be conjecture. So here’s my conjecture.

Music is…

Accessible: People are more familiar with common music apps like Spotify and IHeartRadio because they advertise. I’ve never seen a podcast app advertised.

Easy to follow: Music is often repetitive, so if you care about the message, you have plenty of opportunity to hear it. Podcasters generally have a more complicated message so it’s harder to digest it.

Easy to ignore: Most people don’t care about the message of their music anyway, they are interested in an aesthetic. Podcasts don’t promise a good aesthetic. You have to follow an episode to get the value out of it.

Easy to skip: Finally, you can start a song without feeling like you’re getting invested. When I start a Podcast, I ask myself if I am interested enough to wait until the good part. I don’t think I’m alone here. Music either presents the good part in the first 30 seconds or you can happily skip to the next song.

For podcasting to progress in the future, someone will have to address these issues, either by finding more listeners who don’t care about them or by changing podcasting apps to deal with them.