Why scale the scores?

If we simply reported the total number of questions answered correctly (the raw score), there would be a different passing score for each form of the test (because of those differences in difficulty). This would be confusing to candidates. So, we convert these raw scores to a constant scale such that, say, the designated 75 continues as the minimum score required to pass regardless of the form administered, knowing the number of correct answers needed to pass varies from form to form and from year to year.