Tobias Wolff most likely named his short story "Mortals" because the story explores the theme of people

coming to terms with the idea that one day they too will die

wanting to find out what their loved ones really think of them

achieving immortality by being "big people" while they are alive

hoping that they will have accomplished something before they die

and the realization that no one is above mortality, no matter how successful or powerful they may seem.

Tobias Wolff most likely named his short story "Mortals" because the story explores the theme of people coming to terms with the idea that one day they too will die.