Should they be getting 15% for being a credit card processor for subscription no. The fee is way to high.
My point (which perhaps wasn't so clear above) is that Apple does a lot more than simply being a mere credit card processor.
They hire people to screen through apps, they develop APIs for developers to incorporate into their apps to make them better, the absence of sideloading means a lower incidence of app piracy, resulting in more sales for developers (and consequently, more revenue). Apple has also created a thriving marketplace, both by aggregating the best customers in the world (iPhone users tend to have more disposable income and a higher propensity to spend) and fostering a trusted environment for users to locate and purchase apps (for example, biometric authentication and iTunes means businesses never get my payment information, while Sign in with Apple streamlines the process of creating a new account while still protecting my user data).
The result of all this is that Apple has grown the pie for developers and resulted in more apps being purchased than if the developers had gone at it alone. The implication is that 70% of a larger pie still results in more money being made than 100% of a way smaller pie. In contrast, look at the state of the Google Play Store, which is riddled with scams and malware and brings in way less revenue than the iOS App Store, despite having way more users.
Maybe you have a few household brands who are popular enough that users will jump through any hoop to acquire them (god knows Epic tried to get Android users to sideload Fortnite onto their phones and failed miserably), but for most, there is no denying that it's simply easier transact via the App Store than to host your app on a third party website and hope users will visit it. Apple's value-add is how they have made it virtually frictionless for the purchase of apps.
This is more than what Visa or Mastercard has ever done (they simply provide the backend, everything else is handled by banks). Again, it's debatable how much Apple is entitled to collect for their efforts here, but I can at least make the argument that it ought to be more than whatever the credit card companies are charging.
Allow side loading and apple argument is different. Allow 3rd party app store again different case.
Again, even if users were allowed to sideload apps, would Apple remain justified in charging developers a fee for apps downloaded outside of the App Store? Even if I were to buy a game cartridge for my Switch, Nintendo still gets a cut at the end of the day.
The next questionable part is Apple offers a direct competing product to Spotify which Apple released much later. Now that tax has other things that should be questioned and Apple abusing their position squeezing out competition. It is not a level playing field. Again Apple choose to do it so question.
The problem isn't Apple being in direct competition with Spotify, but that the business of streaming music was never a sustainable one in the first place and at the end of the day, these companies are all serving the same filling.
Even if Apple bears some of the blame for charging Spotify 30% of their users' monthly subscription, why then did Spotify choose to go into this market in the first place, knowing full well that after giving their cut to both Apple and the record labels, they wouldn't be left with anything? This goes back to the problematic Silicon Valley mindset of prioritising market share over profits, thinking that once you have the user base, money will follow. Not seemingly realising that if you are losing money per customer, having more users on your platform just means your costs and your losses balloon accordingly as well.
Spotify also bears the brunt of the blame for conditioning users to expect a free flow of music content at just $10 a month (you can even get it free with ads, or $1 a month via countless promos). If the success of your business hinges on there being zero competition, then you never had a viable business model to begin with, and it was all a house of cards just waiting to fall. If Apple really wanted to drive a stake through Spotify, they could easily have undercut Spotify's monthly pricing, or even offered it free of charge.
The second problem is that what Spotify is offering isn't really differentiated, because it's the music labels who own the back catalogues and new music. Contrast this with video streaming, where each service at least has the option of deciding what shows they want to make, and are therefore able to differentiate their offerings based on content (eg: Disney focus on Marvel and Star Wars, HBO has DC and Game of Thrones, Netflix has Squid Games etc).
Third, another money pit is Spotify's free tier, which is probably costing them more money than they bring in in terms of ad revenue, and Spotify clearly hasn't had much success in converting them over to the paid tier. Notice how Apple doesn't offer a free, ad-supported tier? Maybe Apple is on to something.
Fourth, it's not like Spotify is available only on iPhones. Spotify has well over 500 million subscribers, many of whom are on Android and Windows, but somehow, Apple is singlehandedly to blame for all of Spotify's financial woes, because of their 30% cut which by Spotify's own admission, virtually nobody is even paying anymore?
Apple is nothing more than a convenient punching bag for Spotify to distract investors from the inconvenient truth their business model was never a financially sustainable one to begin with. It deserves to fail.
And fail it just might come 2026 when its $1.3 billion dollar debt matures and if Spotify is unable to service that amount.