I can’t offer a real reason but many of the places that are still on ie6 seem to me to be colleges, schools and some offices the only reason I could gather for it is the technicians are yet unsure how ie7 or even 8 will affect their security and will work with the various filtering software they use.

At least that is the blurb that tends to come from them, cant really see much cause for concern although I haven’t yet seen a full office on vista... (rightly so .. in most cases) so I’m doubtful it we will be shot of it for a while