Windows (also) = job security for computer geeks
Windows vs Linux = endless holy wars for people who have too much time
Network administration isn't cheap. With Linux, you need a geek to keep the network intact. With Windows, you have to pay through the nose for forced upgrades every couple of years (I won't even get into the security issue with MS networks). There was a time when doing business with MS (at least from the consumer side of things) was an ok experience. Those days are just about over. I'd rather deal with a geek who acts cocky because he knows Linux inside and out than deal with a geek who believes that it's his destiny to control every facet of computing.