Why has Debon Logistics Company been recruiting stevedores?

I don't know if everyone has met it. In fact, one reason why Debon has been recruiting stevedores is to find free labor. In the market, I saw a Debon Logistics Center in Hangzhou recruiting stevedores with a salary of 6K~8K, so I went with the mentality of giving it a try. Many people interviewed there, and after they went there, they asked a few words casually, saying that they would try it for one day and let them come over to load and unload the goods at night. Everyone is the same. Then I ask you to sign an agreement stating that there is no salary for the probationers. At night, I still came with a try mentality. As a result, a lot of people came, and each of us was assigned to an unloading port, where we could load and unload goods with regular employees. Besides, we didn't manage to eat, so we went to spend money to eat in the middle of the night. At about 5 o'clock in the morning, the goods were unloaded, and a person in charge called me to the office and said that I would wait for the notice. Besides, most people told me to wait. There are at least twenty or thirty people in one night. Think about how much labor costs Debon can save in a year. This kind of enterprise is really hateful, and you can't help it. He didn't break the law, so everyone must keep their eyes open and don't waste energy and time.