To everything, its own use

I was just reading this book called 'Bringing Home the Sushi', by Mark Meers. In it, he comments:
Japanese housewives, for example, have a propensity for "using certain things only for certain purposes". A person wouldn't consider using a coffee cup for tea, or a tea cup for coffee. I don't mean usually, I mean never. You use chopsticks to eat Japanese food, but specifically don't use them if you're eating "foreign food".
...
You also don't use "eating" chopsticks in place of "serving" chopsticks, or kitchen curtains for living room curtains, or wicker baskets to put magazines in.

This made me think of three things:

One day, Pete was in a restaurant, eating some kind of meat and rice dish. As usual, the meat and rice were served in different, little bowls. So Pete put the meat on the rice and ate them together. A girl at the next table - a stranger - remarked 'wow, that's so interesting, Japanese people would never think to mix the meat and rice like that'. (She wasn't criticising him, just expressing surprise.)


You Should Never Use The Wrong Sauce. If you eat out with Japanese people, you will quickly learn that Certain Foods have Certain Sauces. If you start to use the 'wrong one', people will call out, with urgency, 'no! no! Not that one!!!' To again use Pete as an example, he often protests 'but it's delicious!' and experiment with different dishes and different sauces. No Japanese person would ever do this.


Japanese people have occasionally expressed surprise to see me or Pete wearing short sleeves in late autumn or winter. Even if we're inside and it's like 28 degrees inside (as it often is; a lot of indoor places are really overheated). "Aren't you cold?!" they'll say. But... it's not cold INSIDE... it's so hot we're sweating... yet the stifling trains are full of people fully bundled up in coats, scarves, etc. There seem to be unwritten rules for when and where you don or take off coats, and seasonal rules for whether you wear short or long sleeves, which are not related to the physiological consideration of 'am I feeling hot/cold?'