According to the old custom, when an old man dies, he has to mourn for three years. During the three years, he can't do festive things at home, can't make public, can't post Spring Festival couplets, can't hang red lights, can't go to other people's homes to pay New Year's greetings, can't visit them, can't contact or deal with things outside his own home, and can't enter other people's homes! According to the old man, it's unlucky for someone to die at home, so people shouldn't visit, they will bring bad luck to other people's homes. It's better not to go into other people's homes by yourself than to let other people's eyes explode. Therefore, it is a very important courtesy constraint to prohibit family visits when someone dies.
In recent years, three years has been gradually changed to one year, which has been recognized by people.