For example say you want to buy or sell ore at a barter stand you can only have maximum as the chest size, but say you created an area like a drag and drop and set that to be the area to be stockpiles so if someone sells you 210 ore it will create 3 stockpiles in that area and vicer versa. It can also be used when you are moving lots of soil, stone or bricks you click your wheelbarrow onto the stockpile flag and itll auto take the contents and place it neatly in a spot and when taking away you can still walk onto the area to take from the stockpile. The best example i can think of is from banished
