Because they may have millions of dollars of custom web applications that break when you don't use IE6, and explaining to management why you need to spend tons of money to fix something that isn't (to their eyes) broken is difficult.
Which is why people are uncomfortable with these stopgap solutions existing. I can't speak for anyone else, but I would much rather that this option didn't exist at all, because all it allows is those companies on crutches to keep hobbling.
It's no big loss to the world of technology if some stubborn backwards company can't have its cake and eat it too. They have to either suck it up or lose enough money to realize that it's important. Flex and similar projects draw out that process. Frankly its a negative for everyone in the long run.
