Don't know the official reason, but I've heard that once upon a time the cigars were packed in rows of 8-9-8, much like some are today. (Also, thats the name of a brand which I've never tried). Anyhow, smokes being what they are, tradition stuck. It's like donuts. Why a dozen? and beer. Why 24? besides, I've received some brands where the block of wood smoked better than the cigars!