Its the fucking federal government's policy. Basically it amounts to "pay microsoft as a form of corporate welfare", "permit but not really allow linux", and "this is how it has always been done".

And also because apparently "nobody has ever been fired for choosing Microsoft", which is something that should start happening more often if you ask me

As long as Linux distros have such shit accessibility stories, MacOS and Windows being available should be a requirement for all systems in government.