I'm really bothered by the whole notion of games as less important and "[more] optional". Playing games is a fundamental part of being human, and it is certainly more important than capitalism.
Any game developer could at any point opt out of using Steam and accept payments on their own site, or go through another store. Most developers don't bother because Steam provides enough value to make it worthwhile.
It's impossible to determine if this is the case with the App Store since competitors don't (and can't) exist.