Currency futures exist and are popular. They are popular exactly because central banks can print as much fiat as they want and banks can receive that fiat at low cost and do all kinds of funny business with them on big leverage. This has limited application to bitcoin.

Bitcoin exchanges need to have all (or almost all) deposited bitcoins ready to be withdrawn or at least in cold storage and available at short notice. If a bitcoin exchange introduces bitcoin future contracts, and they get popular and then lends customers' bitcoins to someone for promise that they are returned by the date of the future contract expiry or use those bitcoins to fund some other project, and for some reason most customers decide to sell their future contracts before the bitcoins the exchange lent are returned and to withdraw their bitcoins, the exchange is f*cked, because it can't quickly borrow bitcoins same as a bank could borrow fiat from a central bank.

See the difference with currency futures? Physical commodity exchanges can do future contracts too, because most customers trade paper contracts only and don't ask for delivery, so they would only withdraw cash, not actual commodities. It doesn't work same way with bitcoins. If they withdraw, the exchange has to deliver bitcoins digital commodity to all customers, not just to 1-2% of customers who ask for actual delivery, or declare bankruptcy.

Under those circumstances what's the point of having future contracts in bitcoin from the customer's point of view if they could as well just by at spot, withdraw and wait to sell, and not risk being f*cked by the exchange in 1-2 month when a future contract is due for delivery/expiry?