I can understand- at my last job (multi-national CPG manufacturer) the code on all the internal webpages wouldn't even display in Firefox. Between the IT workload and general paranoia / superstition of execs (any change is bad), there was no motivation to upgrade internal software. So we made all of our suppliers comply if they wanted access to any piece of the intranet. Just easier that way.

For companies that don't rely heavily on internet tech, understanding why you don't want to use IE6 is beyond most people.