During 9/11, many people were told to go back to their offices. Order was maintained. I'm sure a "few" who went back to their offices died as a result. Maintaining order for the greater common good was the intent, whether or not order was actually maintained.

Further, you mentioned that "evacuations are dangerous". If you were in charge of an evacuation, you would have that knowledge in your head. Whether it's a subconscious decision or not, you may decide that it's better to maintain order and endanger a few people, rather than have everybody evacuate at once, cause chaos, and endanger EVERYBODY. Sacrifice a few for the greater common good. It's uncomfortable to fathom, but it's a real possibility, not a conspiracy and not evil either.