I don't have any written or direct evidence, however I worked for a public service broadcaster, who regularly dealt with Apple and Netflix, and the feedback from both was that star-rankings were driving a lot of royalty payments and user choice (people would ignore poorly ranked content). The impact of this was that low performing content providers made less money. By removing the collective scoring, the company would implement their own recommendations algorithms, which gave them the ability to both deliver 'better' recommendations based on what the user consumed and spread the royalty payments more broadly. If what you wanted was to see what everyone else was watching/listening to though, that's not in the interest of their business. Anecdotal and third hand but I believe the people that relayed this to me.