One of the reasons why Japanese use mainly white rice is because white rice lasts longer in storage than brown rice.
Another reason is that they have become accustomed to how easy it is to chew and digest. Brown rice requires more chewing power to properly digest than white rice does.
Finally, many Japanese /Asians choose white rice over brown rice because it is less expensive. White rice is far less expensive to produce and distribute because it is in greater global demand and produces higher profits because of its longer shelf life.
Brown rice takes more chewing-— yes.
Plus with white rice being a stripped food.... You have to eat lots more other foods to supplement it, than you will with brown rice. Modern Japanese subconsciously want to eat more of these supplements (pork, beef, dairy etc) and white rice allows them to. Modern Japanese have the wealth to afford this scheme and same applies to other Asians who have a rising standard of living
I like to buy Thai red rice. A good whole grain rice.
Bourdain in tokyo with the quest for the perfect sushi.
http://www.youtube.com/watch?v=zUBk_w_oZmU
I enjoyed your take on rice and sushi.
http://www.youtube.com/watch?v=R0hH_XR433A
http://www.youtube.com/watch?v=asH4jhr8E20