Not so much...
This may not be as dumb as it first appears. Quite a few large organizations (think corporations, and most importantly, *schools*) skipped the Vista revolution and stuck to XP. That was not a bad move on their part, as a *lot* of software they depend on is browser-based, and some of the browsers did not function properly under Vista for those applications. Java was the main culprit behind this, but that's another issue. By the way, I can think of one major application that will not work with Firefox without *major* tweaking, so sticking with IE is the easier option for most of the school IT departments.
Along comes Windows 7 and now these organizations are seriously looking to upgrade their XP boxes, but are still waiting to see what happens with IE, as their legacy browser-based apps are too expensive to upgrade. IF IE 9 works with these apps, then it is in Microsoft's best interest to tie it to Win7 to encourage these companies and schools to upgrade.
Do individual consumers care about all this? No, but they also really don't care about their browser as long as it works. This decision simply does not affect them very much as the average consumer will just stick with what they know until the buy a new box.
I never claimed to know everything... I'm just right about the things I know!