The issue lies in that most honest "independent artists" do want to go mainstream. They don't want to stay "small" (I highly dislike that word). Hence, they go to the place where mainstream music listeners listen to music: spotify.

I would be surprised if most non-techy folks know about bandcamp. Especially, the older generation who are often not very computer literate and will default to the mainstream option (windows for os, gmail/outlook for email, spotify/radio for music, google for search engine, etc).

Young tech-savvy audiophiles, yes. But everyone else, most likely not.