Dogmaus: bandcamp is niche and drmfree, amazon is restricted and way more popular. Why people releases games on Steam and not here? -_-
I learned my lesson when I changed phone and was locked out of my music collection and Amazon staff said they could not help me...now I don't care, I have preferred to lose all my Amazon tied books, music and Android apps than deal with that. But millions of people will never bother to use Bandcamp. Also, downloding the FLAC files on your phone is not that customer friendly. You have to keep a link and uncompress the file on the phone, many would not be able to do it and it's a hassle.
I used Bandcamp as an example. I could have mentioned Qobuz, which is a quite popular storefront that gets a lot of releases from major music labels and artists. The music there is also DRM-free and available in all sorts of lossless formats. I am not trying to advertise them, I am just saying there are better options than Amazon.
If people want to sell their music on Amazon, fine, but they could try other stores as well. Each time I see music that I want being sold only there, I do not buy it and it is money lost for the artist.