The difference is that Bandcamp doesn‘t need to make deals with major labels. Instead they have smaller and larger labels as well as independent artists coming to them.

I really don‘t understand why Soundcloud tried to get into general, mainstream music streaming. Keeping their niche as paid host for DJs, radio shows, independent artists and small labels should have been their main focus. As a paid service for listeners (in contrast to artists) it simply can‘t compete with Spotify, Apple and others.