It's the one reason I positively hate all the eye candy and executable pages on the web. Accessibility went right out the window at some point, but it was actually a cornerstone of the web that the reader should determine what a page should look (or sound) like.

Now, you could of course craft a page that would still work well on screen readers and that at the same time does the whole dog-and-pony show on more capable browsers. But in practice that doesn't really happen.

Many pages which are in fact just text pages once rendered simply won't render or will render very badly with javascript off.