Hi,
I had a chat with a top security professional in my firm a few days back regarding a similar thing. In his presentation, he had the words "virus" and "antivirus" in almost every slide. So why not erase the problem from root and switch to GNU/Linux or any other *nix based desktop? His answer was simply this "It's client driven. There are some who want nothing other than GNU/Linux and then there are others who want nothing other than Windows. We try to present the alternative to the latter group as it's cost effective for us as well".
Regards,