How many times are people going to get ripped off before randos posting Javascript keygenerators actually tweaks your scamdar? Even if he's not actively ripping off people who use this (and seriously? Why would you think otherwise?!) what makes you think he won't do exactly that in the near future?
The Bitcoin Address Generator page is mainly for developers, programmers, and others that want to double check their Bitcoin Math. The page clearly warns users NOT TO ENTER PERSONAL Private Keys.
Having said that, I am also working on a downloadable version, open source, for use by public interested in generating addresses OFF-LINE.
You should appreciate the beauty in this brand new technology!
I don't see any market need for another random key generator. However, as you say, it is a good check on maths/other generators.
It is also attractive to ppl who have affinity for cards.