On a Cruise ship, if you are invited to the Captains Cabin for cocktails before Dinner you do not turn up in Union jack shorts and a benidorm T-Shirt. You have to wear your Dinner suit, the same as when you go for Dinner on formal nights, or the Maitre de will not allow you into the Dining Room,.
This what you do.
A dinner suit is the greatest social leveler there is , you can be anyone inside it, no one knows who you are, what you are or how much money you have From Billionaires to bin men all the same.
Cheers
Brian