I hate to be this guy but I still feel the science is flawed.
There are a couple diseases that are caused from a lack of myelin.
Multiple sclerosis being the most serious. If we could grow it millions of people would benefit. Do we have an answer on that? My wife is a medical writer and she did a pharma training course on this diseases.
It's a disease, that degenerates the myelin. Maybe it's degenerating faster than it can generate?
From Wikipedia
More specifically, MS destroys oligodendrocytes, the cells responsible for creating and maintaining a fatty layer—known as the myelin sheath—which helps the neurons carry electrical signals.[4] MS results in a thinning or complete loss of myelin and, as the disease advances, the cutting (transection) of the neuron's extensions or axons. When the myelin is lost, a neuron can no longer effectively conduct electrical signals.[4] A repair process, called remyelination, takes place in early phases of the disease, but the oligodendrocytes cannot completely rebuild the cell's myelin sheath.[29] Repeated attacks lead to successively fewer effective remyelinations, until a scar-like plaque is built up around the damaged axons.[29] Different lesion patterns have been described.[30]
Dr. K. Anders Ericsson
http://www.psy.fsu.edu/faculty/ericsson.dp.html
http://neuroanthropology.net/2009/05/20/talent-a-difference-that-makes-a-difference/
Myelin research by R. Douglas Fields
http://video.nytimes.com/video/2007/03/02/sports/1194817108368/the-brains-behind-talent.html
Kai