Put succinctly, the company has gone its own way for so long and now has to support so many developers who use nonstandard Web technologies that it will be impossible to make IE Web-standards-compliant without breaking half the commercial Web sites on the planet.
Hah! Those dumbfuck designers brought this on themselves by not sticking to standards in the first place. Personally, I think they should suffer a bit. And if you haven't convinced a friend to use Firefox (or some other browser) today, you are a slacker.