Because nobody uses it!
i honestly don't understand all the hate around ie.. my experience using it on a day-to-day basis has shown it to be a stable, fast, and well-designed (and apparently quite secure) browser..
[1] http://marketshare.hitslink.com/browser-market-share.aspx?qp...
The number of people using IE9 is on the same order as the entire population of the United States, so regardless of the exact number it's kind of crazy to say "nobody uses it."
i forgot Microsoft didn't release it for XP (which i believe still holds somewhere north of 40% desktop os share), so i can see why that wouldn't be the case.
Have you actually developed any front-end software? I think not...