>It is a common Japanese legend that the truly great itamae-san ("san" is an honorific suffix) should be able to create nigirizushi in which all of the rice grains face the same direction.
While that's definitely an exaggeration, it gives you an idea of the importance of rice in Japanese sushi. Basically, it's taking something that's naturally chaotic (like cooked rice grains that just stick together in whatever fashion), and bring their entropy down to become something ordered by using the most efficient motions possible. For that purpose they use hand fans and wood to control the moisture as well as very finely trained hand motions to control the shape of the nigiri as well as the alignments of the grains.
All of that, just so the guest can pick it up with his/her chopsticks, and have it effortlessly fall apart in the mouth, in an explosion of flavour, like a two stage guided cluster bomb targeting your taste buds ;-).
So, yes, you could probably just use an automatic cooker for the cooking process (although the masters sneeze at that of course, but it sure is standard in Japan nowadays up to a certain price level) - but cooking is the easy part, the fun starts after that.