There is http://TrulyErgonomic.com as well, which has the added benefit of being a mechanical keyboard, It would be the next keyboard I would look at buying (since my current Leopold is giving me a lot of strain during extended coding periods)
They probably want backlit keys or macro buttons.
Many people seem to believe that slanting the keys to the left is actually more ergonomic than a straight "matrix" design. And I think manufacturers aren't willing to risk selling keyboards that don't have the usual look.
The natural keyboard is no different. They sell one idea: splitting the keyboard. The rest doesn't change because it would spur too many questions, and maybe cost them customers.