What's the point of using sugar in savory dishes?
Hot Sour Salty Sweet

Sugar balances both salty and sour flavors in dishes.  Adding just a little sugar makes salty things taste less salty and sour things taste less sour, without actually reducing the amount of salt or acid in the recipe.

For example, the liquid base of the Pad Thai recipe I follow contains chili powder, fish sauce, tamarind, and light palm sugar.  The palm sugar balances out the sour from the tamarind and the salt from the fish sauce.  Without it, the noodles would come out too sour and too salty.

I don't know the physiological reasons for this.  Would be interesting to hear them if someone knew ...