Why? What if you're developing some app where you want to divert from the guidelines, you should be able to do that. Guidelines are just that, they're not rules.
Apps should follow some basic accessibility rules and be functional, but yij can in earnest say that you think that all games for example should follow the Apple design guidelines, can you?
If not following the guidelines makes your app hard to use or glitchy on some of Apple's lineup, I don't see why you wouldn't expect Apple to reject the app. This reflect poorly on Apple because it makes it look that some of their devices are 2nd class citizens within their ecosystem.
They should follow the guidelines when not doing so causes usability issues. If your games is usable on all devices then obviously there's no problem.
Apps should follow some basic accessibility rules and be functional, but yij can in earnest say that you think that all games for example should follow the Apple design guidelines, can you?