The intention of cloud music services like Amazon's (and Google's, and Apple's, and Ubuntu's...) is to provide a convenient way to access your music from anywhere at any time.
No the purpose of cloud players is to keep track of what users listen to.
That tracking is actually a feature that benefits the artist who actually gets royalties when played (which is tracked). This way cloud services like iTunes Match and this Amazon service get to 'legalize' all your illegally downloaded music. The artists eventually (if you play them) get paid fairly.
In the midst of all the humbug about illegal downloading and the music industry going down the drain, I find this a very sympathetic feature.