Its as though someone has told them that sleeping passengers put less demand on the air conditioning (fuel saving) or eat less food. Its not so bad on oceanic flights, but stupid on overland daylight flights, particularly where the flight arrives in the late afternoon local time.
It annoyed me greatly on a Singapore Frankfurt/Singapore flight, and I spent a lot of time looking out from half a blind up by the toilet area.. while cabin staff tried to have it closed. It was high noon and I was keeping an out for them for missiles upbound from the Taliban..
