There was once when I was overseas with my family, and my dad was complaining that the western diet was rather monotonous. "It's either a sandwich with this inside or a burger with that inside. Always bread," he grumbled. After giving it some thought, I raised the notion that Chinese food was also rice with this on top or rice with that on top, which he had to admit was somewhat true.
Having said that, I do think a constant diet of sandwiches is more boring than one of rice dishes. I've considering the reason for this and came to the following conclusion: sandwiches vary less in taste because bread has a stronger taste than rice.
Consider the fact that we can eat bread with butter alone, while rice with only gravy would not appeal to many. This shows that bread possesses a stronger innate taste.
Due to this, the overall taste difference between a tuna sandwich and a chicken sandwich will be less than that between a sweet and sour fish rice dish and a char siew rice dish. If we model it mathematically, it would be as such:
Sandwich - bread takes up 30% of the flavor while the filling takes up the other 70%.
Rice dish - rice takes up 10% of the flavor while the topping takes up the other 90%.
Naturally rice dishes would vary more from each other than bread dishes, making what my dad said somewhat correct.
