In the event of an emergency, people will rush an exit from all directions, forming a traffic jam at the door and causing people to evacuate more slowly. Even if there are tons of exits scattered all around, we tend to all stampede toward the same one because we group together in emergencies -- also, we're pretty stupid. Fortunately, that problem can be mitigated just by blocking the emergency door. That might seem completely backwards, but it's scientifically tested and proven. If an appropriately sized obstacle is placed in front of an emergency exit, then fewer people can try to go through at once, which actually increases the rate at which people can exit. Something large like a pillar, placed slightly off-center, can keep the wave of people dripping steadily through the exit, like an IV filled with screaming idiots.
The pillar also gives frightened people something to pee on.