Why is this concept so difficult to understand?
There are two GPAs: weighted and unweighted. A weighted scale is useful to comparing students within a given school, e.g. to determine class rank. An unweighted scale is (somewhat) useful to compare students within a region or across the country, e.g. for college applications.
Obviously, since different school systems use different weighting systems, it makes no sense to say "I have a 5.56 GPA" to anyone outside the context of your school system. That's what the unweighted scale is for.
It makes perfect sense, however, to weight GPAs to determine the valedictorian, since a straight A student taking AP/Honors classes should be ranked higher than a straight A student taking standard or basic classes.