From Warren Meyer at Coyote Blog, writing about government prioritization:
I will give you my reminder of how to understand most government agencies: Ignore the agency's stated purpose, and assume that it is being operated primarily for the benefit of its employees. One will very often find that this simple heuristic is far better at explaining agency decisions than relying on the agency's mission statement.
In my experience, there are some (not many) exceptions to this: but in the main, I can't argue with his conclusion . . .