mushroom - ////jno has a valid point. //
no ummmm, he doesn't. the flight safety briefing - at least on every flight i've ever taken, using airlines from many countries - says "do not stop to collect belongings".
i've never heard it modified to say "do not collect belongings, unless you really, really, really can't manage without and then we'll make an exception". because then everyone would consider their bag to be important, and everyone would be overcome by smoke before those precious bags were out of the lockers. //
As I have opined previously - you have to allow for human nature in these situations. How people react when they are settling down for a flight, finding their glasses, opening the paper and looking out of the window is a world away from how they will react when an emergency occurs, and they revert to simple natural reactions.
Sadly, as well as getting off the plane a.s.a.p., those ingrained reactions do include getting bags with personal belongings as well - and the ideal notion that people will think not to do that in the interests of safety is simply not available.
You'd like to think that in a pub full of mature adults, if you shouted 'Free drinks for everyone!' that people would form an orderly queue, and await their turn to get a free drink because everyone is included, so there is no need to rush ... but it wouldn't happen!