Thats because the only certainty in life is the promise of death. By accepting it, things in life are put into perspective, and have more clarity regarding worth. However, one only accepts death, when they have a close experience of it. It cannot be a purely rational acceptance.
Of course we die, but to live.. and promote life throughout your life, you shall continue to live after your passing. While not in an earthly conscious form, but a spiritual rememberence shall be endowed upon you to last through the ages...