Why do some pilots leave the seat belt sign on all the way from JFK to Shannon in calm air?
Because it is an excellent idea to do so if you fall asleep (which many people do on a a long-haul), reason being if there is a sudden altitude drop you will end up smashed against the ceiling.
the airlines and their governing regulators need to get it across to passengers that when they enter an airplane they are entering a survival situation and they need to be prepared.
I can see it now in bold black lettering on your ticket: 'GOVERNMENT WARNING: ...' Right
I have flown for 40 years (as a pilot) and as an example, even while deadheading in uniform, I pay attention to the Flight Attendant briefing and I re read the handy information card in the seat pocket ahead of you.
Because you are a professional pilot and certainly well aware of what can go wrong and all of the potential consequences thereof. It would be the extremely rare non-pilot/crew pax which would have that knowledge.
Another round of outrage and angst over passengers acting like idiots in an emergency.
In an unexpected emergency situation which one is not trained for first reactions are purely instinctive; while it would be nice if such were rational and considerate of everyone else that is almost never the case.