MACCA,
The reason is quite simple. I had an old hull around to use as a plug - save me the time of shaping a plug from scratch. The purpose of the excercise was to try some structural design improvements and learn to make tooling for vacuum bag with elevated temp post cure. I already had all the templates. Since then I have learned to make tooling for 350 degree cure at pressure which allows carbon prepreg/ Nomex core construction.
I am not adverse to designing new shapes and have done several. Have to admit though that new fads seem to be over blown. If you put 250 square feet on a 20 x 10 foot cat that
weighs 310 lbs, it will go fast - even if the hulls are shaped like a hot dogs. I don't mean to be irreverant, I have some naval architecture background and understand the technical part. Tornado shape is not that bad. Rocker means more wetted area but also makes quicker turning with less energy dissapation. Flatter section aft would be nice for high speed support where you need it but adds wetted area in light airs. A board with a aspect ratio of 3 is only about 5% less efficient than aspect ratio of 5 (reference is Marhaj; aerohydrodynamics of sailing). It's the art of compromises.

Kevin