I just discovered this yesterday and haven't seen anyone post about this. The dimmer switch in our cars to the right of the steering wheel has two buttons, up and down. In Park, adjusting this will also adjust the brightness of the ambient lighting in the doors. Once you put it into drive it dims but turning down the gauge cluster brightness in drive will also completely turn off the ambient lighting.

 

You don't want bright interior lighting at night 'while driving', thus in Drive the lighting dims. That is also why the NAV goes dark mode in low light conditions.