His Grand Company of Eorzea dream is a reality, and the main threat to it now is the destruction of the star. Will he go out like grandpa and leave a heavy weight on his twin sister? It could possibly breech whatever has daddy's cheeks clinched so tight. So much pathos-laden regret to fill a series of cutscenes.
Well, if you play with the Trust for Shadowbringers the game understandably uses what made sense for each phase of the story, so that early dungeons still feature a name in the dialogue text that a character no longer uses.
Even if characters retire or fade away into obscurity, wouldn't they be unavailable after that point for dungeons that come after any that?
Imagine if a favorite Trust member dies, though, and the only way to see them again outside of the storybook of cutscenes is to run old dungeons with the Trust.