The main purpose of the old whaling industry, as you can read about it in Moby Dick, was to get whale blubber to render into lamp oil. Whale oil was better than any other illumination-fuel available at the time. It was rendered obsolete, and the industry mostly killed off, by the introduction of petroleum-derived kerosene, and gaslight, and, much later, electric light.
There is still some whaling, especially in Japan, but, as I understand it, nowadays the purpose is to get whale meat, not blubber. Does anybody anywhere hunt for blubber any more?