It's been shown that in life-or-death emergencies when seconds count, the vast majority of people simply freeze. Psychologists call it normalcy bias - our higher reasoning functions shut down amidst overloads of ambiguous information and danger and we convince ourselves for precious seconds that everything is fine. Stopping to get your bags is a version of normalcy bias.

Investigators of the Tenerife disaster (where two 747s collided on a runway) found that many people on the PanAm plane died in their seats. Survivors mentioned seeing people sitting calmly in their seats as the plane burned.

There's a really fascinating chapter of David McRaney's book You Are Not So Smart on normalcy bias where he goes into the Tenerife disaster in detail. Highly recommended. He says the way to ensure you are one of the people who gets up and goes is to consciously rehearse what you'd do in an emergency before an emergency happens, so your higher reasoning doesn't have to figure it out in the heat of the moment.