That doesn't make any sense. Are you arguing that because Apple sells things that work on Apple devices, they should not charge anyone anything to use their infrastructure to reach that user base?
Yes, Google music competes with Spotify in the play store. Google and Spotify both pay publishers about the same amount and both have revenue of less than 30% of the $10 coming in. Google doesn't compete with Spotify by charging them a 30% cut they cannot afford or by forcing Spotify to jack up their prices above the market rate.
Tell me how it benefits you as an ios user that there are no music sub or ebooks you can buy at the market rate in ios other than Apple?
It's an anti consumer practice that takes advantage of prevailing publisher rates to push the competition out of offering IAP and leaving Apple as the only option instead of just building a better product.
Let me guess, you were fine with apple colluding with book publishers to jack up eBook prices also.