If you use water ice in an icebox to keep things frozen then the ice cream will melt as fast as the ice cubes and likely get soggy in the process. Dry ice sublimates into carbon dioxide gas at a lower temperature than the freezing point of ice cream, so it’s a much more efficient way too keep things both frozen and dry if a bulky plug-in freezer isn’t available. I’m guessing this is a big concern for airplanes as well as mobile ice cream carts.
The obvious trade-off is the safety hazards posed by dry ice, which the people who serve the food are ultimately responsible for.
