The bottlenecks in their escape were the doorway and the
crew's deployment of the inflatable slide... why wouldn't
you grab your bag if it was readily accessible?
Wrong. In order to be certified airworthy, you have to be able to evacuate an airliner in 90 seconds, in the dark, with some of the emergency exits blocked. Here's an A380 doing it: http://www.youtube.com/watch?v=4TAkAcQOnQY
The whole thing now makes me wonder if there was some very deliberate reason for their egress to be delayed. Something having to do with fire or the risk of fire? (I really have no idea)
Here's a 777: http://www.youtube.com/watch?v=4TAkAcQOnQY
If everyone stops to grab their bag, it can take ten times as long. If the plane is on fire, then people die.