There less than an hour in between the South Tower being hit and it collapsing. In that time a lot of confusion and terror reigned. People in the impact zone and above the impact zone were not even sure if they should go up or down. Many believed that the whole area below them was impassable and so headed up towards the roof in the hopes of being rescued by helicopter. IIRC most of these people had never had any evacutation information given to them or any drills conducted. People may have only had an imperfect sense of where the stairwells were. Trying to find them in an environment which might be filled with smoke and debris would have been difficult. People also likely had debates about what to do. And it would take time to take one stairwell down, find it blocked, take it back up again, try another, etc etc.

1. Just 4 people escaped from above the impact zone in Tower 2, not 16

2. Stairwell A was possible only after clearing debris. According to Brian Clark many people turned around after trying to descend A stating it was blocked.

3. You are making an assumption it was possible for these people to reach Stairwell A.

At that moment of the tragedy the men and women in the tower at various storeies were in a state of mental aberration and fear of death and every one wanted to escape from the tragic incident as quickly and effectively as possible. The idea of using the staircase from so much height is also clipped with a question mark. The stair case downward takes time to reach at the ground level and hence all men and women tried to run away and escape from this tragic tower, which was hit by the aeroplanes and caused so much havoc and disaster first time in the history of US.

Because Bush.

And Clinton.

The towers were blown up by the Islamic Fascist Enemy, and not "George Bush," despite all of your wonderings and wishful thinking.

Why did so many people failed to escape from Stairwell A? Stairwell A was the only stairwell that wasn't destroyed when Flight 175 hit the South Tower. Only 16 people successfully escape from above the impact zone using that stairwell. 200 people went to the top of the South Tower in hopes of helicopter rescue. If I was in the South Tower after the second plane hit. I would be checking all the stairwells in case one wasn't destroyed, in which one wasn't before going to the top of the building.