The Federal Desktop Core Configuration as written by the Office of Management and Budget (OMB) governs how an agency sets up their computers. Of course with any large organization and trying to write one size fits all policies there will be issues.
At the US Department of Agriculture's Cooperative State Research, Education and Extension Service (CSREES) it was recently decided that only Internet Explorer would be used as a browser. Unfortunately one of the jobs of this organization is to develop web sites for the USDA. At a minimum in order to test them one would try to load them in other commonly used browsers. With Firefox, Safari and Chrome making more-and-more of a market penetration you can see why this is a problem.
On the face of it this is a typical problem and criticism of government. A faceless bureaucrat implements a policy arbitrarily and without any thought. One hopes that with some negotiation the policy will be restructured to allow the necessary testing. The problem is one of scale. There are hundreds of thousands of employees with a like number of computers and laptops that need to be managed. Flexibility is limited to a point because it just makes sens to standardize as much as possible. That is why the majority of the Government uses Microsoft and Windows products.
It is also hard for a manager to show much independence in these types of areas through fear of being punished. There is zero tolerance almost for any security breach or problem and the training received by employees over-and-over again stresses this. Sometimes there is little imagination in the Government.