First of all, talk about those who seek money. This is the most obvious and direct purpose. After the Spring and Autumn Period, I don't know who started it, and the custom of thick burial became popular. Some poor people began to try their best to gain benefits from it, so the wind of grave robbery gradually prevailed. After all, looking at the gold and silver jewelry that is considered ownerless in the tomb is still very exciting for people with bad lives.
The second is revenge. China has paid more attention to filial piety since ancient times. What if someone wants to avenge their relatives or friends, but the enemy has passed away? Dig their graves, drag their bodies out and whip them. According to historical records, Zixu avenged his father's death, dug Wang Ping's grave and flogged Wang Ping three hundred times. There are many such examples in history.
Finally, there are strange purposes such as ghost marriage. Ghost marriage has a long history, probably starting from Shang Dynasty, and may still exist in some backward areas. If someone dies at a young age, family members hope to find a male or female body that also died at a young age to match the yin marriage. Before, there were some bad behaviors. Some people do this for a living, especially those who rob a tomb to find a body to match a yin marriage. What is more frightening is that it is not enough to find the body from the grave, so they found another way to make illegal things.
In fact, there are still some motives, such as finding a tomb with good feng shui, but finding that people have been buried, digging them out and trying to seize this treasure trove of feng shui.