Just the idea of people springing onto evacuation slides while very high above the ground (757 or larger) is a very serious option. If a slide fails to inflate etc, people might jump or fall anyway if they panic, or are pushed, when the "reptile brain" takes over in those behind you. Now if fire trucks are quickly next to the plane and tower control gives you their radio frequency, they can help decide if there are flames coming OUT of the engine. A little smoke from an engine and/or brakes, wheels while quickly being sprayed by a fire truck, might not require a very hasty, risky evacuation.
Broken legs, arms or necks could result from any evacuation, even from a much lower (to the ground) MD-80 or 737.
[This message has been edited by Ignition Override (edited 31 May 2001).]