I don't know, but one reason might be history. Modern insurance companies are pretty recent. Before the 1920's, there were mutual-aid societies. Commodities trading is ancient.
But they also do different things:
You need insurance companies for one-off risks. Someone has to go see the house and say, "yep, it burned down." Also, we don't let people bet on other people's houses burning down for good reason.
Other risks are more impersonal, like "what if this company I bought a bond from goes bankrupt" or "what if the price of corn drops in half" or "what if the price of oil doubles." There are lots of people and companies who might want to hedge against those, not just the owner of the property.
But they also do different things:
You need insurance companies for one-off risks. Someone has to go see the house and say, "yep, it burned down." Also, we don't let people bet on other people's houses burning down for good reason.
Other risks are more impersonal, like "what if this company I bought a bond from goes bankrupt" or "what if the price of corn drops in half" or "what if the price of oil doubles." There are lots of people and companies who might want to hedge against those, not just the owner of the property.