they do. and the way it's supposed to be done on night flights is lights kept on but dimmed. the cabin should never be in total darkness, so the crew can see what's going on in the cabin should someone say, keel over in the aisle and have a heart attack.

that being said, most crew do TURN OFF the lights so people can sleep. even if the op were to complain to AC about the lights not being switched off, and AC tried to reprimand the purser, he/she was just following AC procedure. stupid, as there is always enough ambient light from galleys, reading lights,... to see what's happening on the plane.

as for the screens, they can be dimmed or turned off....