Wouldn't this end up leaving even more money on the table? Spotify pays artists based on their share of total plays.
Say two sites (X and Y) join up to offer a $10/month pass for unlimited access to both sites, with the say pay scheme as Spotify. Site X has 3 times as many articles/videos as Site Y. If every user reads/watches 100% of Site Y's content, Site X may still receive an equal or larger share of the payouts even though users consumed a much lower percentage of it.