Read up on the onion futures markets; due to a (rather fascinating) historical decision, they are one of the few commodities without speculative futures. As a result, price volatility in the market is massive, with far worse swings compared to the efficient markets where speculators operate.

I challenge you to write out what scenarios you think reducing market participants will solve. Historically it has 100% so far been highly illiquid markets with huge price spreads, which is terrible for both sellers and buyers.

What you’re suggesting means a farmer selling wheat futures for delivery a year from now needs to be at the market at the same time a bread maker is looking to buy wheat a year from now. That basically doesn’t happen because the bread maker doesn’t need that level of forward looking price stability.

That is how they were in the beginning. I recommend reading about the development of markets and futures trading to see what benefits they provide, as they are a component of any developed economy around the world.