It dawn on me that alittle over a year ago when I took my son who is an aviator in the air force on a short cruise just before he was deployed overseas I understand clearly why all of our military branches have such sharp formal dress uniforms when he wore his on formal night :
Next time you are on a cruise and you see a member of our armed forces in their dress uniform on formal night watch how other guest react around them and to them
It is quite appropriate for members of armed forces who are on active duty to wear their uniforms for the "formal" evenings aboard ship. This topic seems to come up pretty often, and was the subject of a relatively recent thread on the "Cruise Dress and Packing" board. Nonetheless, I'll provide the basic information here to save digging.
In the United States, the uniform regulations of all services stipulate that the members are to wear the uniform that's equivalent to the attire prescribed for civilians for social functions of this type. The current uniform regulations of the respective services prescribe the following uniforms and substitutes. The Air Force regulations seem less clear than those of other services as to when various uniforms are worn, so I'm taking an educated guess as to the prescribed substitute.
>> U. S. Army: White Mess; substitutes (in order of precedence): Army White with Bow Tie, Army Blue with Bow Tie, Army Green with Bow Tie (enlisted only)
>> U. S. Navy and U. S. Coast Guard: Dinner Dress White Jacket; substitute: Dinner Dress White
>> U. S. Marine Corps: Officers -- Evening Dress B; substitute: Blue-White Dress A; Staff NCO's -- Evening Dress; NCO and below: Blue Dress A
>> U. S. Air Force: Mess Dress; apparent substitute: Semiformal Dress with Bow Tie
Uniform regulations in most other countries are similar.