Because the palace is too big and crowded. Although many people think that the palace is heavily guarded, there are guards everywhere who often take turns guarding it, and there are many eunuchs and maids walking around. But the palace is not as small as tofu. There are many palaces and buildings in the Forbidden City, some of which have been unoccupied for a long time, and some are still far away. The guards in these places often have loopholes. There are many people in the palace, so people may come and go with dirty hands and feet. Moreover, it is difficult to distinguish people in different palaces, and it is also possible to mix in a few thieves.

Modern people seldom know the size of the palace. There are not only many palaces, but also large areas and many people in them. There may be dozens or even hundreds of imperial secretaries in a palace, not to mention the people who usually go in and out of the palace. It is actually very difficult to manage so many people. If one of them steals, as long as the stolen goods are hidden by him, it is difficult to find the criminal. And usually just throw some small things, the palace manager and guards will not specifically investigate.

Secondly, the communication between people in the palace is also very complicated. For example, maids can leave the palace at the age of 25, but some people look for opportunities to steal things after leaving the palace. In addition, the palace often needs to be repaired, and some craftsmen are likely to sneak into the palace to steal things. In addition to these two situations, some agile and daring thieves will also come to the palace, but these people often come to show off their skills and deliberately run around the palace, leaving a sign to visit here.

To sum up, the safety of the palace corresponds to the palace of the emperor's concubines, who are the central figures in the harem. And the more remote the place, the looser the garrison may be. Coupled with the frequent and complicated flow of people in the palace, it is normal to occasionally have a few fish that slip through the net. The last thing left is another situation, people who deliberately provoke the emperor.