Because China’s no different, and geopolitics don’t map well onto personal relationships, except that trust matters. Even in your example, it would be that the drug dealer attacked and stole from my great-great-great-grandfather, and now the drug dealer’s great-great-great-granddaughter is returning the property. It’s a bit foolish to treat her with the same level of distrust, and it would be even more foolish to be the one to break the agreement if I know that I will have to keep doing business with her in the future.