In addition to affecting the temperature and dilution of your drink, ice absorbs the flavor of anything it's exposed to in your freezer. So those cubes that have been sitting around, uncovered, for who knows how long? They're definitely giving your drink a funky taste. W&P's main motivation in developing the Peak Ice Works line of ice trays was to help home bartenders make great ice at home, bringing you that much closer to recreating cocktails made by the pros.
(Also, giant ice cubes look really cool in your cocktail or mocktail.)