Because Japan obsesses more over cleanliness than America. Their schools don't even have janitors. The students are expected to clean the classrooms and other areas in the school themselves. I think it has something to do with Buddhism. I could be wrong, though.
Vietnam actually has the freshest foods/markets in the world. You want a fish? Go over to that tank filled with swimming fishes and pick out the one you want. Feeling like eating frogs? Be careful with this one. He's a jumper.