It's not arbitrary, the appstore is a de-facto monopsony, the ordinary user doesn't install apps from anywhere.
Most Android phones come with an alternate appstore installed (e.g. Samsung come with their own one as well as google play) and you can easily install others.
To install alternates on the iPhone you have to root it.
In the 80s, the game console makers did not operate the store where you were buying games. Even, you could buy second-hand games without Atari or Nintendo receiving any part of the fee!
Even back in the 80s, the console makers “controlled distribution”. Nintendo forced third parties to use their manufacturing facilities and they all force third parties to distribute their haves with a license key.
Console makers have always forced third parties to pay a fee to distribute their games.
