What's the point of setting off firecrackers at a funeral?

When setting off firecrackers at a funeral, people over the age of 80 must die of natural causes. There is a title: Happy Funeral! That is to say, after the age of 80, the elderly have poor physical function and often get sick or something. Normal death is equivalent to going to another world to enjoy happiness. In some places, the troupe will be invited to make trouble on the day of the funeral. Setting off firecrackers in our place when sweeping graves must meet the following conditions: 1, 10 years later; 2. There are happy events at home. For example, when grandpa dies and grandchildren get married, they must go to the cemetery first. It is ok to set off firecrackers at this time.