Why is carbon dioxide gas added to a draft beer system?

In a draft beer system, carbon dioxide gas plays a crucial role in maintaining the required pressure to dispense the beer effectively. When the pressure is appropriate, it allows beer to flow from the keg through the lines to the tap without excessive foaming or other issues. If the pressure were too low, it could result in flat beer, while too high a pressure might cause over-carbonation and excessive foaming. This balance is essential for serving beer at the desired quality and ensures a consistent pour for patrons.

Other options, while relevant in certain contexts, do not accurately reflect the primary reason for the addition of carbon dioxide in this scenario. The focus is squarely on pressure maintenance, which is critical for the functionality of a draft beer system.