We always used to stress that passengers should "keep seat belts loosely fastened around your waist whilst seated" - more often than not, this sound advice, along with the safety briefing, were completely ignored back then & sadly, still are to this day.
These days, as a passenger on flights, I see people looking out of the window or wearing headphones, sleeping & worst of all talking, whilst the announcement is in progress.
These people never even tell their kids to pay attention.
No gimmick announcement has ever worked including the BA one because when people have seen it once, they ignore it next time.
You can lead a horse to water......