That is a good question, BillRM. Let me give it a shot.
Short term speculation in a commodity such as oil is considered "bad." Politicians and some economists deride the impact it can have on markets. That is not the issue that I am talking about here.
Suppose though that you are the US Postal Service or FEDX. Fuel is a big component of your cost. You can't go changing the price of a stamp or the cost of delivering a package from Amazon on a daily basis. You need to set a price for the next year. So you (the USPS or FEDX) have economists who try to project where the price of oil will go in the next year and then you sign contracts (with speculators) to get that oil at a set price.
If you at FEDX come to a different conclusion then the economists at UPS, you may win or you may lose. So it goes.
Does that make any sense?