In the pan...
'Mozilla removed support for an Adobe plug-in, saying it had "degraded the performance of the browser to the point where it didn't meet our standards."'
So, if you're frugal with platform's CPU you don't want something hogging the cycles.
Why doesn't Steve just tell us that's why the iP....s won't do it either?? Heck even my Atom N270 powered netbook stutters at flash.
Well, it's obvious really: omnipotents don't see the need to explain.