[klodolph]

You may be reading a lot of value into this distinction. To me, as an American, equality in a peer relationship is important but bookkeeping and debt is destructive. The 50:50 split is just an ongoing division of labor, it is explicitly NOT debt because it never accumulates. Any "thank you" is an acknowledgment of gratitude or merely a polite exit to a conversation one doesn't want to continue. The debt that children have to their parents is to be paid to the next generation.

It's another one of those cultural quirks that seems more telling than it actually is. For example, because Russians don't smile to strangers, they're cold and unfriendly. Or because Americans do smile to strangers, we're untrustworthy and insincere.

The reason we think it's so big is because we're translating the literal contents (smile, "thank you") but ending up with a completely different meaning or set of pragmatics. and then we miss the ability to use set phrases in our native language. Just like you can say "pleased to meet you" in Enhlish, but you can't say "よろしくお願いします".

Edit: to clarify, cultures are different and language reflects that, but I think a lot of set phrases reflect history more than they reflect living culture.

[billjings]

Upthread someone mentions Graeber's _Debt_ book. You might find it interesting. It has a whole discussion on exactly these set of phrases. They were not always with us, and it's interesting to see when and why they came into common usage. In a large part it was out of the need to have economic transactions with strangers, and the need to not be tied up so tightly with our families.