I have black out curtains, as my (& my wife) are both nocturnal. I have had complaints from visitors (my mother, in particular [& she has good night vision]) that our home is "cave-like" in it's usual lack of lighting.Problem with projectors is the screen must, by definition, reflect light. Blacks cant be any blacker than the screen is with the projector off, in the ambient light conditions.
So for good image quality they need to be watched in close to total darkness.
There are small lights at low outlets in a similar fashion to the down near your ankles movie theater lights that come on when they sense motion.
Since that is our normal way of life (we typically go to bed after sun-up and do not go outside before 4:00 PM [unless we have some sort of appointment]).
So, for us, that is not an issue, once we get back into a big enough space to do that.