Originally Posted by
Iscah
The other reason (if you care about such things) to do it is some background/worldbuilding lore about Nanamo's parents and an old alliance with the Amalj'aa. You could get most of it by following a few specific paths – one run starting from each of the three doors from the beginning, then the specific combination of actions that unlocks the bonus boss and true ending, plus reading the journal entries from a wiki instead of the game.
Although that is assuming you only need to do the bonus boss to get the concluding quest, and don't need to run every route. I'm not certain about that.