They're first and foremost for safety, and there are codes prohibiting - for this very important reason - keeping anything out on the fire escape. However, we've all encountered their use as a small outdoor escape, be it for catching a cool evening breeze or as ledge for placing flowers and plants:
These fire escapes are just a few that show folks putting them to use in such ways. Inhabiting fire escapes as a balcony or placing any object on them is illegal, though we still see this frequently and - while we don't advocate it - we always take notice when we spot a little sign of life on a fire escape. We're reminded of A Tree Grows in Brooklyn and the story's young Mary reading books out on the fire escape of her parents' apartment.
Have you ever had an apartment with a fire escape?