That should be covered by the one time fee that developers pay to Apple in order to publish apps into the App Store. I am not sure if a simple binary needs a 30% cut of the entire Spotify profit to keep up with the costs of hosting an app there.
> Why? They've made the hardware. Why should they have to let Spotify run on it in the exact way Spotify wants? (You can Airplay Spotify to Homepod.)
Because Apple is using a completely different market, which they have a strong presence on, to increase the value of Apple Music and consequently devaluing any other competing music streaming services.