A. I don’t buy into the “duopoly” argument. Other options do exist, and just because two options are the most popular of a variety of options doesn’t mean it’s a “duopoly”.
The duopoly here is the Apple App Store vs. the Google Play Store. That's where you'll find the apps you
need to access banking, authentication, the major online services etc. A smartphone is as much use as a chocolate teapot without one or the other. Increasingly, the browser-based versions of those services, where available, are losing functionality (e.g. my online web banking asks me to use my mobile app to verify things - there are alternatives, but they're a major hassle in comparison). Likewise, for developers, if your app isn't in one or both of those stores, it probably isn't going anywhere. Yes, you can sideload in most Android implementations but you usually have to jump through a bunch of user-unfriendly hoops to get there so it's not going to be viable for the majority of users.
Apple has, pre-EU-intervention, made the App Store the
only way of installing Apps on the iPhone. Google, pre-EU intervention, only allowed third-party Android systems to include the Play Store if they also promoted the rest of Google's (data slurping) application suite (effectively turning everything into a "Google experiece" phone). While that stands, there's almost zero chance of a competing App store getting any traction.
en.wikipedia.org
Once you get to the position where there are only two of three "most popular" players owned by large corporations then
without regulation those players will engage in anti-competitive practices to protect their popularity.
Apple created and own iOS, iPadOS, etc.
...and thereby effectively created the smartphone app market, fundamentally changing the IT landscape. When the App Store started you didn't need a smartphone app as the lowest-friction way to access your bank account or pay for parking. It's a case of "with great power comes great responsibility" and without regulation large corporations have no other incentive to take any of that responsibility if it would detract from their main legal duty of increasing shareholder value.
If Spotify really thought Apple’s terms were unfair, they could make their app for Android and other platforms and either completely ignore Apple’s platforms, or have iOS users use their web app. They don’t have to do business with Apple.
Whups... I'll just leave this here:
From:
https://en.wikipedia.org/wiki/Spotify
In July 2015, Spotify launched an email campaign to urge its App Store subscribers to cancel their subscriptions and start new ones through its website, bypassing the 30% transaction fee for in-app purchases required for iOS applications by technology company Apple inc.
[snip]
in the following months, Spotify joined several other companies in filing a letter with the European Union's antitrust body indirectly accusing Apple and Google of "abusing their 'privileged position' at the top of the market",
[snip]
The complaint led to the European Union announcing that it would prepare an initiative by the end of 2017 for a possible law addressing unfair competition practices.
We don't know what Apple's current deal with Spotify is or if they're still paying 30%.