Why do we need memorials?

I think that we need memorials is because that people can be remembered by greatly for something that they must have done. Cementaries have plaques for those who die so that their family can remember that person or the descendant. For example the memorial of the Vietnam Wall for the fallen during the war. It hows how so many people lost their lives just because of it. I think that memorials honor people in a way so that they can be remembered and that they will not disappear. If there are no memorials then everybody would just basically disappear and be nothing and won't be heard again after ho or she died. That's what why I think that we should need memorials. If that person might have been close and died then that person might've cried every time that nothing in the world think he or she exists since there are no memorials.