To put it another way, SoundCloud at its core is a free streaming site, and it also allows free downloads if enabled by the music act. There is no way I know of to set up SoundCloud for paid downloads or streams. Thus, using Bandcamp, Spotify, iTunes, Amazon, Tidal, Google, Deezr (etc) are wise to capture a modest revenue stream and listener data in ways SoundCloud simply doesn't support.
SoundCloud a lot more like Facebook than it is iTunes: socially important, great for sharing, a way for something to go viral - all important angles in modern business, sure. Is it such a monolith that I'm worried about its future? Not really; it'd be sad to watch it crumble (further, in some respects) but that doesn't seem likely for at least a couple more years. Lots can change.