Remember though what happened when Apple told developers that they could only use web app for the iPhone? There was an uproar because developers---good developers at least---want to be able to make use of all the features that make a platform unique.
That's why we live Cocoa + HTML5, or Android SDK + HTML5, etc... If you want a common cross platform target use HTML5, if you want to make an app that feels like a good citizen on the platform and makes use of the latest innovations in said platform, you use the native SDK.
It's all about the right tool for the right job.
And Flash is inefficient, controlled by one company while at the same time not being a good native framework. Basically you got the worst of native SDK and the worst of HTML5 and put them together... and you expect people to be impressed by that???