That would be a more fair criticism if Apple charged the game publishers fair fees commensurate with the cost of security audits, bandwidth, availability, and the like. Instead, Apple (and other app stores) tend to demand massive profit sharing.
App Store transaction fees amortize the costs of development/operations of not just the store itself but the OS it all runs on. If you pay 99¢ for an app that covers re-downloads and multiple devices in perpetuity. All running on a global CDN with exceptional uptime.
Apple doesn't charge users a dime for new iOS upgrades over years of the life of the device. Even years old devices get the latest software features of new iOS versions. Supporting old devices has a non-zero development cost.
Considering how Apple makes almost 50% hardware margins on every iPhone sold, I think they make plenty enough to continue software support off the initial hardware sale alone.