Like people of any country, the Japanese used the resources they had in as various ways as imagination would allow. They also grill, cure, steam, smoke etc. fish. These mightn't be as famous as sashimi, but are just as much part of the cuisine. The clean flavours of raw fish and the minimalist presentation also suit the typical Japanese taste, although which came first is anyone's guess. In a country where it's impossible to be outside of walking distance of either the sea, a lake or a river, it's hardly surprising that fish forms a large part of the diet, and that freshness is an affordable luxury.