An important function of the mourning process is to

An important function of the mourning process is to help prevent grief-stricken individuals from committing self-destructive acts.
After a loss, especially if it was somebody really close, people tend to be very depressed to such an extent that they may hurt themselves badly or do something even worse, like commit suicide. This is where other people come in - they need to take care of that person and be there for them so as to avoid any further casualties.