What's the result of the completely useless flight safety mantra? People will not leave their belongings! The mantra should tell them that they will be compensated if they make it out alive but they will be put down like a mad dog if they hinder others with their packing and packages...
Also people do charge all the fucking time, and don't put their phone into airplane mode. :|
I would say it works incredibly well. Everyone knows what it is. Everyone knows what they are supposed to do in an emergency. Everyone knows there are emergency exits. Everyone knows there are life jackets. Everyone knows they are supposed to wear a seatbelt. At least some people will get it right.
Do not underestimate how even minimal training can be extremely effective at scale. I know from experience that I am a person who does not freeze, I focus. When shit happens, I act but I can act without thinking. Because of that mantra, I have a plan to follow and I will act correctly.
Also don't underestimate the effect of priming. It reminds you there is a plan. When pilots prepare for takeoff, they briefly review how to handle emergencies during takeoff. Not because they don't know, but to bring those procedures to attention and have them ready in their mind.
For the mantra to work, all it has to do is remind you those procedures you vaguely know exist.
Also people do charge all the fucking time, and don't put their phone into airplane mode. :|