The root cause here seems to be fairly clear: (Excessive) vertical integration of platforms (or rather their owners) across domains.
The duopoly of mobile app stores would not be nearly as problematic if it wasn’t also tied to a duopoly in phone OS vendors, one of which also tied to a monopoly in phone vendors, which is tied to a monopoly (quasi-monopoly? not sure what to call iMessage in the US) in instant messaging platforms etc.
The duopoly of mobile app stores would not be nearly as problematic if it wasn’t also tied to a duopoly in phone OS vendors, one of which also tied to a monopoly in phone vendors, which is tied to a monopoly (quasi-monopoly? not sure what to call iMessage in the US) in instant messaging platforms etc.