The Bread-Rice Dichotomy

Up-down. Right-left. East-West. Male-female. Light-dark. Bread-rice...uh, what? Exactly. Yet I need two hands (and maybe a foot) to count the number of times that I've been asked "which do you like...bread or rice?" As if the world is divided along a bread-rice culinary axis. Japan is the only place I've been where I've heard of bread and rice being pitted against one another like this. Why is that? Is it an extension of the self-Other dichotomy (the Japanese version being a Japanese-Foreigner dichotomy)? Rice is a Japanese food, bread is a non-Japanese food--does that render bread and rice opposites?
Mark points out that, when people ask him this question, they show surprise when he answers that he likes rice better. This leads me to believe that the question of one's preferred carb source is really a question of cultural identity. So when Mark says he likes rice better, or when I say I like both equally, what are we REALLY communicating about ourselves? I have no idea, but I have a feeling we are conveying some sort of message. Maybe next time I'll say "actually, I like neither. Potatoes are my favorite" and see what people think...