Why I think BTC futures is a scam?

I'm no analyst and could easily be wrong, but if the CME and whatever other company is not required to actually hold the amount of btc that they are trading short or long for, then what exactly are they even doing? Place a buy order...for what? If you want to cashout..what are they cashing out? Just trying to profit off the price listed on a real bitcoin exchange? Are they just betting on numbers at this point? From my understanding, if you were to buy a bitcoin future contract with the CME, you must fund your account with enough to cover the current cost of 1btc. Ok..but you are not even buying 1btc. You are placing a bet on their that the price will change somewhere else. What if the exchanges they base the price on get hacked? What happens to your contract? What about the fact that they have an open and closing time for trading? If your selling price hits during the time they're closed..then a few hours later the market corrects you lose. I guess I just don't understand how they are allowed to do this without having to hold the amount of bitcoin they are having people "buy" at a certain price and then sell later. Can I start an exchange for trading Large mouth bass in Lake Michigan? You buy at the quantity there are in the lake, then sell at what you think the quantity is at a future date if 1 bass = $1 ? You wouldn't be able to take the quantity of bass you paid for home with you if you just wanted to HODL it..so what are you even paying for? Guess I just dont get it...the media attention spreading awareness for bitcoin is all well and good, but this futures thing to me seems kind of dumb.

Image source: cmegroup.com