Why is demand history irrevelant for the management of raw materials and work in process?

Discussion Question number 2 on page 397 in Chapter 16 of Operations Management, Contemporary Concepts and Cases (Fourth Edition) by Roger G. Schroeder has a typographical error of omission which is questioned by many online business students who use the textbook and are asked by their instructors to answer this discussion question which should read:

"Why is dependent demand history irrelevant for the management of raw material and work-in-process inventories?"

The answer can be found very early in the chapter, but it would be cheating to try to find it on WikiAnswers simply by typing it in!