What is the purpose of using rice vinegar and sesame oil in sushi?!
Answers:
The main purpose of using rice vinegar is adding flavor and also some acidity that will open up the palate, which also serves as a contrasting element with other ingredients in Sushi(Sushi means vinegared rice in Japanese).
Another reason for adding rice vinegar traditionally after it is cooked is to preserve the rice and prevent any food borne illnesses associated to it which is caused by bacteria called Bacillus Cereus.
Sesame oil is not a main ingredient in Sushi but it can be used in small amounts to add a characteristic aroma. Instead mirin is used to supply a balancing sweetness to the sourness created by the rice vinegar.
http://www.ecolab.com/PublicHealth/BCereus.asp
It's used for for flavor. A lot of asian dishes use sesame oil and rice vinegar.
The same reason you put anything into any recipe.....the flavor!!
