There are large amounts of state spending information that is hidden. Some reasons for this are basic. Governmental divisions are focused on their required functions and little attention is paid elsewhere. Why would it when there is no incentive since government workers tend to get standard pay increases? And if one does pursue some innovative thinking, they risk a likely backlash from the status quo work culture.
But there is another reason that is not so innocent: those who purposefully keep data under tight control so that they can cherry pick it to support policy goals and hide defects.