A bright panel can be turned down.
The ones that don't have more expensive electronics driving the backlight. Eizo's FlexScan EV series is one example.
I have a FlexScan EV, and I don't find being able to turn the brightness down to 1 or 2 nits without any flicker as useful as I thought I would. Even in complete darkness, it is hard to read the screen when the brightness is that low.