There have been billions of dollars poured into government software that runs on Windows. Billions more poured into support, verification and validation of that

There have been billions of dollars poured into government software that runs on Windows. Billions more poured into support, verification and validation of that software. Switching would be very, very, expensive - and its not clear that it would help even in the long run. Additionally, Windows is still THE dominant platform for science and engineering work, especially modeling and simulation. How many engineers (non-CS) do you know that do not use Windows? The most popular CAD software, SolidWorks, is available only on Windows. Alibre, the second most popular one, is also Windows only. The next most popular one, AutoCAD, is Windows and Mac only. 3DStudio Max - Windows only. Most simulation software is also Windows only, at least when I was a government contractor, that was the case. If the government switches to Linux, they'll have to switch en masse - having some people on Linux and others not won't work very well at that scale of bureaucracy. And when even most engineering software isn't available on Linux, that isn't gonna happen.