I think "banned" is an overstatement. There were/are people obligated to use Windows because they need professional EDA tools and suchlike software only available for that platform. And although it's by no means my speciality -- I'm a distributed systems developer, not a Windows sysop -- I was told a few years ago that the general belief was that Windows had the most sound security story of all the operating systems you could put on a laptop. The reputation of Windows is a combination of history and the fact that idiots are likely to use it, so it always looks like the OS people do stupid things with. But if your company culture isn't stupid you can make it work much better.