We have one widebody type of aircraft in our company and at one time three different cabin and exit layouts, and different exit types in each part of the aircraft type in some cases. I doubt if it is possible for a regular customer with us to completely remember and memorise all of these.
It's politeness and good manners to watch the briefing whether you are customer or crew, on our smaller type I quite often stand visible in front of the customers whilst I read off the demo and 99% of people watch, its far more personable and gains fuller attention than a video demo.
For those who don't, you are quite likely the ignoramuses that will probably cause a problem during an evacuation through your lack of situational awarness and knowledge of a particular aircraft's layout or safety features/equipment, and could possibly kill others and yourself through your ignorance in the event of an emergency.
I'm not sure that anyone not watching should be subject to the threat of arrest/action unless they are being disruptive, I think that there are far too many cabin crew that are a bit too quick to steam in with ultimatums when they are simply not required and when a polite couple of words will usually suffice.