Because Bandcamp is perfect at this and nobody can beat them.
I say that with tongue in cheek, but they have been the platform for average musicians to self-publish on for a while. They've even totally foregone their cut periodically during the pandemic to help artists. And unlike Spotify, artists are able to apply their own branding to their pages. I've never met a musician with a bad thing to say about them or their platform.
One reason is due to flat rate bundled compulsory licensing. If you run a coffee shop with live music you either restrict all performers to only play original works and still probably get threatened with lawsuits, or you pay up the ASCAP/BMI/SESAC protection money and can play whatever.
So in many contexts weirdo obscure independent artists can't compete on price (e.g. give their music away just to get it heard) because the customer has already paid for a bundled rate for popular music.
Isn't that just "radio"?
The fact that individuals aren't able to break out via self-publishing music is an oddity in the internet age. Why aren't there more avenues to hear "random new artist that matches my tastes"? or is it self-perpetuating that labels sign all successful artists who can go mainstream?