Value-Destruction in Controlling : Why is Efficient Controlling Difficult?

The controlling department in companies most often has to deal with at least partially different requirements from different stakeholders, complex systems and environments. This, oftentimes goes along with tight time lines for provided analyses and extensive use of error-prone, manual auxiliary calculations in spreadsheets to deal with the above mentioned differing requirements in a flexible manner. Thereby Controlling bears the risk to end-up in a situation trying to fulfill its tasks (or the ones Controlling believes to be its tasks) without knowing the cost of doing so.That is, within Controlling complexity is adding up that has significant impact on output quality and/or required resources and thus, marginal cost of Controlling might outweigh marginal benefits which translates to the fact that parts of Controlling become value destructive.Does this really happen in the area of Controlling, being the function of a company that should enable management to prevent value destructive undertakings? Is Controlling's own backyard not taken care of (enough), and why? What can be done?