don't these folks realize that this is exactly the same functionality as a native web plugin... or simply a "download & install" button? Or Silverlight? Or Java? Or a good Javascript interpreter?
Of course they do, but the big difference is that other companies own/control those technologies, and coming up with your own system means that you won't be at their mercy down the road.
Silverlight means lock-in to Microsoft, Java means being dependend on Sun's whims, etc.