The Cunard line is definitely a different sort of cruise line these days. I'm surprised that they still haven't relaxed their dress code.
I believe that they have a different clientele who like to dress formally.
Carnival Liberty New Year's Eve 2007
Liberty of the Seas 5/2008+11/2009
Allure 1/16/ 2011
Vision OTS 2-14-2015
Freedom OTS 3/6/16