Why does xrandr output brightness setting not persist? Is this a bug?

Run

xrandr --output eDP-1 --brightness .4

Download an attachment in gmail in chrome. The brightness resets itself to 1.

All kinds of other random moments kick the xrandr output setting back to default, so I run this command several times a day, just to have non-blinding monitor backlighting.

For example, closing the lid and opening the lid will also default back to insane-bright.