[hylaride]

My theory is that they don't have the incentive. Apple Genius was ridiculously good at music discovery, too. I shudder to think how much I spent on iTunes songs via genius over its run. But now that apple/spotify/etc get my monthly dollars either way, there's no huge incentive for them to create the discovery systems.

[HDBaseT]

The incentive (for Spotify) is to make you consume the least amount of media, since every stream requires CDN and Bandwidth costs, plus royalties.