I agree entirely that it is the height of rudeness (and stupidity) for passengers not to put down newspapers etc to listen to safety briefings. From recent flights on a number of airlines, off duty crew travelling as passengers are big offenders.
If an off duty crew member does not feel the need to listen to a safety briefing - which invariably includes a passage along the lines "We appreciate you may have flown frequently ..." what encouragement is there for other passengers to do so?