The futures market's were set up to allow companies to hedge on future prices commodities. In other words the Users and Producers of commodities could go to the NYMEX or CBOT and trade contracts with a price set in the future, this was done for cost of production planning purposes. The key word here being HEDGE, not speculate. Speculation started creeping into the market in the early 1980's with the advent of computer based trading. Speculation is nothing but gambling that prices will move in one direction or the other. For example at point in the summer of 2008 Goldman Sachs owned contracts for August and September delivery that could never have been delivered because they represented 10 years worth of production. Those contracts had no relation to the actual physical commodity thus it was speculation. Part of the reason the investment banks and hedge funds started chasing commodities, they were looking for returns that could not be had in the stock market.
Until the early 1990's futures contracts that were written by companies or individuals that did not possess the actual commodity or use the commodity for production were taxed a lot higher on any gains that were made trading those contracts. That law was repealed at the end of George Bush I.
sorry for the long post.
David Knapp