Quick reference: http://www.amazon.com/Mis-behavior-Markets-Benoit-Mandelbrot...
He did a paper on the price of cotton in exchanges obeying a 1/6 power law. When confronted with this, the powers that be said, effectively, "we don't have the tools for that" and didn't use any different tools than they were using to measure risk. See The Black Swan for more examples.
Markets don't fit normal distributions.
I suppose it comes from having to justify what your doing to higher up managers who don't have the time or inclination to learn something new. I mean, if you can't explain it in 30 sec they won't like it.