the only thing i can think of regarding jeans in the public areas is that the dress code for Formal Nights involves the entire evening, not just dinner. You get dressed-up and you stay dressed-up for the entire evening. You will find yourself in the minority if you decide to go to a show , bar or casino on formal nights in your jeans. On a personal note - Formal Nights are so amazing on a cruise, its really an experience not to be missed(imo) you don't have to break the bank on clothes either all you need is a nice long black or navy skirt with a silk or glittery top and dress shoes. All the men need is a nice dark suit, dress shirt/tie and dress shoes.