If you've been using a phone at night at max brightness since 2011ish, chances are you have no rods left in your eyes and you're blind unless its at max brightness.

Like how people who blow their hearing out with loud music turn up the volume to continue to hear the music. It's a destructive cycle.

Personally, auto brightness can't get dim enough at night, and indoors during the day it's annoying seeing the brightness shift everytime the lighting changes even a little. It's great if you're in the sun tho, it can go brighter than the manually set "max" brightness.