People have been trading commodities for thousands of years. Even these days, the commodity market is unique due to having physical, real-world implementations. They are the most affected by the real–world events, which often leads to the most lucrative opportunities for the traders.
For example, if oil reservoirs are in surplus, it is likely that prices will drop accordingly. And if there was a drought in South America, you may expect the prices of the coffee beans to spike. There is logic to this market, which attracts many investors that are willing to trust their wits in order to make a fortune.
Additionally, some commodities are considered safe-haven assets, meaning they can add stability to a portfolio which consists of highly-volatile assets. For example, many foreign currency traders turn to gold futures when the market becomes too volatile, as gold prices are more stable overall, while still growing at a substantial rate.