I ended up with IE8 because I ran Windows Update, not because I had some desire to get a new IE.
My guess is that most Windows users are going to let the updater run, and get new versions of IE.
Exactly. Chrome updates faster because it does it with zero user input. It just happens whenever spare resources are available and politely lets you know when it's done. IE8 needs you to run Windows Update, which a significant number of users don't want the hassle.
I think we're each arguing from incompatible anecdotes.