Which is exactly why a place like SoundCloud does make sense. Young artists need discovery and YouTube isn’t optimized for music discovery. It does an okay job at it, but compare it to what Spotify does: not on par. Plus, to really succeed on YouTube, you need some kind of video which increases the artist’s cost.
I know several people who use SoundCloud for discovery in the background while doing other stuff in another tab. Executed well, an all-audio service does make sense (even as a business, though likely not one as big as YouTube’s). Particularly, if you think about the mobile experience where YouTube, frankly, sucks.
Also: Even though you disregarded Podcasts at the beginning, I’d beg to differ. It is a great market opportunity. As I wrote in my SoundCloud piece the other day: Ben Thompson had a great piece on the issue and you basically just need to exchange Apple with SoundCloud: