Mr Optimistic, I don't think you understand what people are trying to explain to you. As former cabin crew with three airlines (including BA), the commands we practice for an evacuation drill include "get out, leave everything behind", yelled at the top of our voice, as we "gently" push people in the small of the back, down the slide. In our annual recurrent drills, some crew (sitting as passengers) are asked to take baggage to the door during the emergency evacuation, and within seconds there is a line of people that can't get out as the crew try to make the passenger leave the case behind. Leave the case by the door, the exit is blocked, do we tell the passenger to return the case to the overhead locker ten rows back?!
Many passengers find it impossible to obey the fasten seat belt sign, listen to the demo yada yada, and perhaps it is these same people who choose to ignore the yelled commands "get out, leave everything behind"
But I have to say, who knows what we would do in a panic. We may not react the way we think we would. Tossing the cases over the side of the slide isn't an option, as there may well be passengers under there, or emergency services. But taking cases away causes a line of blocked passengers in seconds.
Personally I think the crew did an amazing job, and I am just glad I retired with nothing more serious than helping out with a few faints and panic attacks.