I understand the logic and don't have a particular problem with putting my book down, just wonder why some cabin crew (appear to) create their own rules...

If this was something important for safety, then surely it would be mandatory everywhere (or at least somewhere).

I agree, by the way, with the post suggesting exit rows should not be left empty, although I can't think of a flight that wasn't so full that the exit rows were at least "manned" at the window and exit, if not the middle seat.

Slight off topic (but hey, it's my topic ), I was on the evening flight from AMS to GLA last week and another pax was moved to the exit row just before we took off. He had to be sent back to his original seat and replaced during the flight when the crew realised how drunk he was...