NJ:
Probably because no one ascribes to it within our resident creationists. You have to remember that the VC theory has been antiquated now for a number of years. Anyone who subscribes with AiG or ICR probably dropped the theory at their behest.
All YEC 'flood geology' today perpetuates ideas first given widespread attention in
The Genesis Flood by Whitcomb and Morris (1960). This is the book that put a 'global catastrophic flood' into circulation as a catch-all explanation for geological phenomena. By making YEC seem more scientifically plausible it slowed a previously growing trend amount religious conservatives toward OEC and theistic evolution.
The 'vapour canopy' was an important feature of Morris's argument. Another was that humans and dinosaurs existed at the same time--an argument supported in the book by references to Carl Baugh's 'giant human footprints', including this photo:
The book was not an attempt to do science but an attempt to make the Noah story sound scientific. The 'vapour canopy', Baugh 'footprints' and mineral dating claims have been withdrawn by AiG. In the decades after the book was released, new discoveries in plate tectonics and genetics rendered its claims not just pseudo-scientific, but antique.
YECs are keeping the book's ideas on life support, though, which is why we're here. They have been forced to acknowledge plate tectonic theory. After an initial attempt to invoke miracle--the continents and mountain ranges were created as is, with only an appearance of having been moved around--apologists were obliged to make tectonic activity part of the 'big muddy mess.' This further compresses an impossible series of geological events into a year's time. The approach to genetics has mainly been simple denial. The hypothesis of distinct biblical 'kinds' was falsified in the 1980s. We know that genetic 'kinds' do not exist. Discoveries confirmed evolutionary theory and offered a new window on its driving mechanisms.
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Edited by Archer Opterix, : brev.