Not true. There are those that speculate with futures contracts, but every buyer has a seller, and every seller a buyer. Unless you can actually make delivery or take delivery of soy beans, you must clear your speculative position before the contract date. It is a zero sum game for speculators. They keep the market price fluid, but cannot really change the overall price--that is all supply and demand driven. Cheap dollar also has no impact. Where in the world did you get such strange ideas about the commodity markets?
Future trades are certainly not zero sum. There’s always a spread.
There is more volume in calls then in put option - these are really executed and create a lot of demand at a certain time. As you say you have to clear it - buy actually buying.
What was ment as a price ensurance drives demand. Not the real demand.