Jimmy - excellent post, as always, but I feel your logic is beyond the grasp of some.
Interestingly, we are on Sky this Saturday, out of Southampton, and the roll call on another social media group, is full of chatter about how people are looking forward to getting dressed up. Lots of photos of dresses and tuxedos being posted.
I think that there is an increasing divide between the US philosophy of "I'm on holiday and will dress how I want" and the UK philosophy of "I'm on holiday ,so will dress differently and more smartly to how I would do normally ".
And who am I to say which is right !
As an aside, I have booked a cruise today with a small UK cruise line - their dress code states, amongst other things, no polo shirts at night ! But, their ship, their code!