No one needs a rating system really. We are on a stock music site ! F.e. you sell a track very good and a customer comes suddenly to the idea to rate the track with 0 or 1 star, no matter for what reason he did that. You go down from full 5 stars to maybe 4. In the future you will sell less of this track. I promise. It`s simply pure manipulation and no one needs that. My opinion.