I like how the explanations get more and more complicated just because you guys WANT to disagree with the Occam's Razor answer: it can't be replicated, which is why it has value in a world where nearly everything can be replicated by the transformation from energy into matter. The technobabble explanation as to why it can't be replicated is not even important at all.
It really is the most simple and logical reason.
Um... we know it can't be replicated.
The question is "WHY can't it be replicated", not "CAN it be replicated".
The question is just as important as anything else in the show.