Steamed fish cuisines like this one are made without any oil. It is sort of curing / pickling process, hence fish can be stored for couple of days. In old times when there were no refrigerators people who had no daily fish market nearby, especially from the inner parts of Kokan, developed these recipes so they can enjoy their fish without having to go out to the market every other day.
Malvani people are so much in love with sea food that it is pretty hard for them to bear wet monsoon months when supply of fresh fish is limited. They find some relief in dried fish and prawns. During summer people buy these dried fish, especially small size prawns called jowala, that they use as an alternative to fresh fish during rainy season.