Okay, so I have to put it away - your argument is logical and compelling. But why do I have to turn it off? (And tangentially can anyone tell me what the safet

Okay, so I have to put it away - your argument is logical and compelling. But why do I have to turn it off? (And tangentially can anyone tell me what the safety grounds are for opening the window blinds? (Or is it just to make the turnaround quicker by not requiring cabin staff / cleaning crews to do it before the next flight boards?))