Why do Asian savory recipes call for a few pinches of sugar? I've got a few Asian recipes (e.g. Mongolian lamb and Singapore duck) that request only &#8539; teaspoon of sugar for a meal fit for 2 or 3 people. That feels too little to affect sweetness.

Are there particular ingredients common in Asian cuisine that require de-acidifying with sugar, or is the sugar used for another purpose?
First, there are plenty of sour ingredients in Asian cooking, that are de-acidified by a little sugar. Tomato paste, peppers and soy are examples that come to mind.

Second, and this is the Zen-style answer, is that the sugar is to sweeten the dish a little. One teaspoon of sugar in a sauce is plenty sweet enough, especially if you're not used to having 6tsp of sugar in a can of Coke daily. Sweetness, like saltiness and spicyness, is something we get used to easily.