There is also set of standard user expectations, and a general design culture that ties the platform together for its users.
On top of this is the massive investment that Apple has made in educating users of what to expect from the platform -- an investment that is further strengthened each time a user uses an app that follows the expected conventions.
Further, users buy their phones for this cohesive platform experience. If they wanted flat UI, they could buy a Windows Phone. They haven't.
So yes, forcing a completely non-standard UI on users, and promoting its use on the platform, is condescending and honestly hostile to the health and cohesion and shared value of the platform.
And then, perhaps, we will preserve one of the things that has made iOS, and Mac OS X before it, such a pleasant platform to use: platform consistency.
Oh, the horror.
The first Apple HIG was published in 1977 for the original Apple II. It was written by Bruce Tognazzini: http://en.wikipedia.org/wiki/Bruce_Tognazzini#Background
He and his partner, John David Eisenberg, wrote Apple Presents...Apple, the disk that taught new Apple II owners how to use the computer. This disk became a self-fulfilling prophesy: At the time of its authoring, there was no standard Apple II interface. Because new owners were all being taught Tog and David's interface, developers soon began writing to it, aided by Tog's Apple Human Interface Guidelines, and reinforced by AppleWorks, a suite of productivity applications for the Apple II into which Tog had also incorporated the same interface.
And thus interface standardization was born, out of the cumulative, compounding benefit of fulfilled user expectation.
As developers, it's our job to be the wizards behind the curtain. The users are the star of the show, not us, or our egos.
1) be less rude in your pissing on other people's work they offer for free.
2) Wake up and smell the HIG-is-obsolete coffee, the HIG has been not important for the most successful apps for years, and even Apple has toned down their insistence on it half a decade or so ago, including making tons of apps with different looks and even feel (from the iTunes vertical close buttons, to Dashboard widgets, to the totally different Pro apps Look and Feel ever since 2007 or so, to the App Store UI, to numerous other examples all around).
Gruber (an old fierce supporter of the HIG back in the day) has written about this:
http://daringfireball.net/2011/01/uniformity_vs_individualit...