Using Steam is even MORE optional. They're PC games! Yet people still want to be on Steam even if you have to play by their rules, because being on there creates value.
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.
I don't think that's the point that was being made - Steam is optional not because the content on it is games, but because the content is PC games - i.e. content where there's no obstacles to distributing it yourself, or through other stores.
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.
