Well, for one, because it is a very popular food there in Japan as well as it is Kishi's favorite food to eat. He said he eats all types of Ramen, giving Naruto and his friends, a love for it as well :3
I'm pretty sure that ''what they eat'' is not even part of the plot? DAA??!!? Or maybe Kishi needs a private chef in his team to work on everyday meals they serve to charecters once in a while.... NO ONE CARES