In fact, much of the defense against Mr. Ricci's reverse discrimination lawsuit consisted of the allegation that the test wasn't customized enough: the consulting firm had borrowed a question from earlier tests that referred to "downtown" when there is no downtown in New Haven (or something like that -- all I remember is that the lack of local customization of one question was a big deal in the national press for a couple of weeks in 2009.)
One reason is because a large number of the people who understand this -- professional I/O psychologists -- are employed to come up with new tests that will do what 100 years of I/O research says can't be done.
* By the way, once every century the learned dons of All Souls College stage a drunken torchlight parade while singing the "Mallard Song" about a giant duck devoured by their predecessors in the 15th Century. They are led by the specially chosen "Lord Mallard" (typically a distinguished classicist or a future Archbishop of Canterbury) who waves a duck on a pole. The last Hunting the Mallard was in 2001, while the next one will be in 2101.