Why do we want to leave something behind after death?

I am now collecting materials to write my personal history. First I didn't want to leave anything behind my death. I am merely a common man, and I haven't done anything great that I brag about. But,recently my wife suggested that we write our personal histories respectively. Hearing her suggestion,I began to realize that everyone living in this world has lived his/her own special life. The course of my life is unique and different from any other's in this world. What I have done so far is great or not,that does not matter at all. My life is different from others. That is why it is worth writing my history.