So a government writes a constitution that has one word. Breathe, and you don't think it should help it's citizens? I know this is an extreme and higly unlikely example, but it makes a point that not every possibility can be accounted for in a document, even a living document that can be amended by the people as things will come up that prompt the amendment, but will need to be addressed before said amendment is written, voted on, and applied.
So while I agree that the U.S. Constitution shouldn't be outright ignored (as our courts have been want to do on occassion), I realize that somethings weren't thought of by the founding fathers or by the wise men who have set into motion the various amendments since. Considering a new amendment hasn't been submitted since 1971, that's a significant amount of time in the developed world (yes, I know the 27th was ratified in 1992, but it was originally proposed in 1789, 202 years earlier, and took forever to get ratified).
So what do you think we should do when wading into previously unheard of territory? Just ignore it and shove our collective heads in the sand? That's what constitutionalism would have you do.