Pax/CC discipline
I've also noticed pax are slooowly getting better at keeping their belts on. But IMHO it is not-so-subtly discouraged by cabin crew who ignore seatbelt warnings.
Sure, many do the right thing, and of course there are phases of the flight where the CC are supposed to be walking around whilst the pax are belted up.
But surely everyone here can recall cases of CC sitting on jump seats doing not much without belts on? Pax see this, and (a natural human instinct) feel that if they (the CC experts) don't bother, then why should they?