This was technically understandable.
SoundCloud made their website to LISTEN tracks for free and POSESS tracks for purchase. BandCamp also made their website for same motives by same features.
And... I think you already guess what happens on two.
Actually I embeded BandCamp widgets on the top of this website I thought most of people listen and a few percentage of listeners would purchase them. But as a matter of fact, 95% of listeners of 'Alice EP' series purchased the EPs. How could it be achieved by SoundCloud widget?
I think the biggest difference between two music player is the primal reasons of made for. The primal reasons of two service providers effect design of the widget somehow, and listeners involuntarily act to achieve the primal reasons.
Technically, both two services have download purchase feature, but to tell about widgets, only BandCamp has 'Buy' link. Two widgets have really similar features except that link.
In my idea, download/physical purchase is not rely on motivation of possession. In BandCamp, we feel that the site was MADE FOR purchase, and SoundCloud make us feel the place which was MADE FOR listen. That's what let us purchase or listen.