White labels and dubplates in general hearken back to the sound system culture that originated in Jamaica [1]. Mostly a means of getting the newest songs fastest; record something in the morning, press your dubplate that afternoon, play it out that night. The unofficial nature of the recordings makes it easier to hop around copyright stuff and not clear samples, etc. The song Alicia by Mala jumps to mind [2], I don't think it's ever seen a proper release because of the heavy use of Alicia Keys samples.

1. https://en.wikipedia.org/wiki/Sound_system_%28Jamaican%29 2. https://www.youtube.com/watch?v=zpV7radKuwo