This probably has a large amount of 'survivorship bias' embedded in it (no pun intended).

People who are frantic, time-critical, but not immediate life-threatening situations probably grab their bag (ie. the landing gear on plane has failed, but plane has stopped on runway intact and not on fire).

This probably differs significantly if the plane was ripped in half, or people were choking from thick toxic smoke. Those people probably don't even think about grabbing their bag because they are in active severe pain / dying.

Point is, people are making a rational decision that "This is a dangerous situation and I need to get out of here, but I will probably survive", therefore they take their stuff with them.