You still have fragmentation though, which creates surfaces for security and privacy issues that the 'wild west' of the 2000s had. OS providers could enforce standards for these 'stores' as a fix, but then they'll be accused of unfairly regulating competition.

Part of one of the antitrust suits against Google was that it required Play Services to be preinstalled by manufacturers on Android phones before the Play Store could be preinstalled - but the latter needs the former to work.