a lot of people still use old hardware with low memory and disk space that won't run anything above XP. until they replace these with newer or more capable hardware, they're stuck with what they have now. it's not upgrading the OS only. it's upgrading the whole system, hardware and software. and for less affluent people, it's not something to do every 2-3 years.
I like how I can just type an internet address in the address bar of windows explorer and be browsing from that window instead of opening a whole new window. But then I use FF for all the browsing. The company does not allow users to install applications themselves, but provides all with FF and even upgrades it once in a while. IE6 stays there for the "some sort of prompt for some custom db bullshit" when and if the page needs it. But IE6 is not restricted, and it's up to the users to use whatever they want, and the users seem to like it, and the IT department goes "meh, whatever"