Because it's not an agreed standard, because it controls how I see it not the other way around, because it doesn't fit into the concept of interconnected web of documents, because not everyone has or wants to run flash.
I am not against all flash, it's ok for a little bit of extra decoration/fun. I am against when the only way to view a website is with flash. I mean wtf is wrong with the scrollbars that the browser has why does every idiot flash "webdesigner" wants to put all his text in a tiny little box with its own scrollbar that doesn't work as well as the one my operating system provides me?
Sorry to totally derail this but Flash is an insiduous presence that must be fought.