I personally like to have a "choice" in cruise lines and dress. Oceana has all CC casual, NCL has Freestyle and other lines have traditional but whatever the dress is the cruise lines need to SET IT, COMMUNICATE IT and ENFORCE IT.
It may be your vacation but it is also the vacation of the other people who are on the ship and have decided to adhere to the dress code. The tone of the venue and the evening is set by the dress. While it may seem trivial it has a significant bearing on a large number of people who do adhere to the guidelines. The cruise lines have an obligation to enforce those guidelines and maintain the atmosphere they have set with guidelines.