Apple has a competing product which it favours dramatically its own platform. That’s a cause for not only complaint but also intervention.
I hate analogies, especially car ones, but it’s like Apple selling a car, then only allowing the owner to buy petrol from a specific petrol station. Once at the petrol station, they offer their own petrol, which is ‘optimised‘ for the car in a way no other petrol has the option to be optimised. They offer this special petrol at the top of the list, with other ’gimped’ petrol below. They charge a flat fee to be allowed to offer petrol in the first place (siting special access to specific knowledge of the car, which they hide in the first place) then they charge a fee per litre on top, neither of which is applicable to their own special super petrol.
Maybe I don't understand the complaint.
Yes... iPhones come with Apple Music installed. And some people might say Apple Music works best on an iPhone.
But clearly the hundreds of millions of Spotify users with iPhones have figured out how to use Spotify on their iPhones.
If Apple was preventing other music streaming services from being on the iPhone... then that would definitely be a problem. But you can install and use many different streaming services on your iPhone.
Apple includes the Notes app on every iPhone. Does Evernote complain about that? Bear Notes?
Apple also includes the Podcasts app on every iPhone. Does Overcast complain about that? Pocket Casts?
Maybe they do and the press doesn't cover it since every week there's a new Spotify complaint... I dunno...