Why a Motorola Razr instead of an iPhone 4S? Because the latter didn't exist. When IE6 came out more than a decade ago, it was the absolute best browser available. In 2004 when XP SP2 came out, it cleaned up a lot of reliability and security issues. You just have to look at IE6 with a 2001-based lens and realize what the alternatives were at the time.
IE6 was good enough to become the standard for slow-moving corporate types, and they're sticking with it. The every-few-weeks upgrades of Chrome and (now) Firefox are way too fast for them.
A lot of these big companies will stay with IE6 till the bitter end in 2014, when free XP support (security patches) goes away. I wouldn't put it past some of them to pay for XP support rather than switch to another OS, or to negotiate extended XP support into their Microsoft upgrade contracts.
Anyway, there's enough non-IE6 work to do that I generally refuse to write any IE6 code (and when I do, I don't spend more than a minute or two copy-pasting some conditional comment found via Google.)