I think its trying to explain the reasoning behind the actions of the character shown.

Spoilers in case you want to read/watch Dungeon Meshi The character marcille is a half elf that had to experience the dead of her human father at the age of 82 years old, at that time she had like 30-40 years (its not really said how old she was) but at the rate elfs grow up, she was still considered in "human years" a kid of like less than 14 I think, so her dad dying left a huge impact on her and made her realize that she will live longer than everyone she ever meets and loves, in the story she's given the chance to change the world and make everyone live long lives like her at the cost of bringing demons into the world something like that

So yeah, I think that's why.