You do realize that it is in the interests of Apple/Google to have these websites optimized for WebKit and not HTML5 generically. Of course it hurts non-Webkit browsers and that's the point. The idea that Apple is an open-standards company is the most laughable thing ever. They are just about the most proprietary company ever.
You do realize that it is in the interestst of Microsoft to have the entire WWW optimized for Internet Explorer (4-7) and not HTML4 generically. Of course it hurts non-Trident browsers and that's the point. The idea that Microsoft is an open-standards company is the most laughable thing ever. They are just about the most proprietary company ever.
See what I did there?
As an aside. WebKit originally came from the Browser packaged with the K Desktop Environment. App Apple did was contribute a ton of changes to it to make it better. Anyone can implement a browser on WebKit and you can even use a different JavaScript engine if you want (like Google has done). WebKit is open source, and it has the kind of Marketshare IE6 had during it's height.
It's dumb to not assume developers will target the browser engine with ~90%+ marketshare in mobile and not the one that just hit 1% well over a year after release.
iOS
Android
BBOS
WebOS
Symbian
Bada
All use WebKit. Anything else is an afterthought and will be investigated on an as needed basis when it makes sense to devote the resources to doing so.
The pain WP7 users allegedly feel is wholly Microsoft's fault, and nothing different than the pain Mac/Linux/Solaris/whatever users felt back when half the internet didn't render properly if you weren't running Internet Explorer. That lasted like a decade, and not developers are very apprehensive of doing anything "special" to support Microsoft's browsers.