TLDR: Why do people choose soundcloud as a place to upload their music? What is it's function? Is it there for easy embedded players on social sites? Is it there so randoms can see what you have downloaded? I don't understand its popularity to be honest, but then again I haven't used it much.
It's actually a really good community for musicians to share their work with each other. The utility may not be obvious to chip musicians that already have their community websites, but Soundcloud is used in a lot of way by other musicians that do not have such communities:
- Record labels use it to accept demos & showcase upcoming material in their catalogs.
- Musicians use it to share stems, loops & field recordings for collaborative works, and to find these things from other musicians.
- they also use it to share demos, bootlegs and free tracks.
- they also use it for online storage, streaming, and for cool looking (& customizable) music players to put on their websites and on social networks.
- they also use it to share private tracks (demos, work-in-progress, etc) with others for constructive criticism.
That last point is probably the most useful feature for me.