Because the futures contract needs to be delivered when it expires, that is, the seller needs to register a qualified physical object as a warehouse receipt to fulfill the contract. However, if the seller fails to organize the warehouse receipt for delivery on the due date, it needs to pay liquidated damages, which is about 20% of the amount. Once the registered warehouse receipt is obviously insufficient, bulls often use it to push up the price, and bears can only close their positions at a high price without physical delivery, that is, squeeze positions. This usually happens when short-term spot prices alone judge the high futures price.