Because philosophy and silly opinions like Dr Shulman's are purely daft thats why.
The massive amount of brain energy required for consciousness is, believe it or not, created by a working brain. When the brain stops working, the energy disappears, just like pulling the plug out of your PC.
You said in another post that the PC still has 'potential energy'. But that isnt the case with the brain, because after it is dead it is no longer working, hence it cannot reform your consciousness.
A dead brain would be more comparable to a dead CPU. Once dead, they do not contain, or at least make use of energy anymore, and the power / consciousness that they once provided is completely gone / destroyed.
If you want to research or learn about consciousness, then I would strongly suggest that you study Neuroscience instead and learn about how the brain and its nervous functions and impulses actually work.
Heres a book that I strongly suggest you pick up and read:
http://mitpress.mit.edu/catalog/item/default.asp?tid=8595&ttype=2