After an intensive conference day, you need relaxation, laughing, talking and of course something to eat and drink. A conference is not only important for what you learn from tutorials and presentations.
Meeting collegues is at least as useful.
The social event will be the way to meet your collegues in a informal setting. As much as possible, the original appearance has been preserved. Several hundreds of candles make sure we can see each other. Finally, a ventilation system makes sure we get all the fresh air we need. Of course, there will ample to eat and drink.