Exactly. And look at how much of a nightmare it is every day! Fortunately on the web it is very useful. No need to invite that pain into an environment designed for replicating the printed page though.

And the thing is, the html spec doesnt include js. It specifies a way of marking it up. Thats not the same thing. The core pdf spec actually contains features so powerful, you could almost make a lisp machine out of them. See the video for details.