Why do cocktail mixes contain milk solids?

Upon scanning the ingredients list on my bottle of Daily’s Sweet and Sour mix, I stopped on ‘milk solids’ and couldn’t imagine why their inclusion was necessary. Some recipes for sour mix include egg whites to give the drink a foamy texture, but I’m not seeing that here. My only guess is that the lactose cuts some of the burning sensation of whiskey. An email to Daily’s yielded only my inclusion on their mailing list.