This is just speculation on my part, but I've wondered if it's because of listening patterns: I tend to listen to entire albums at once and did most of my discovery on Spotify by starting "radios" from songs or albums. Spotify would then rabbithole me on those even when refreshed; they'd slowly converge on the same set of songs, unless I moved to a completely different genre (and even then I'd sometimes end up with playlists with all kinds of discordant stuff mashed together).

I got fed up when I looked up while working and realized that I had listened to Circles by Dag Nasty[1] like 8 times in a single day. I used to like that song, but now I can't listen to it anymore!

I've switched to Last.fm, Bandcamp, and my friends (bless them) for discovery.

[1]: https://www.youtube.com/watch?v=Vyx4JeyMJE0