The decision on appropriate attire is up to the people in charge letting me on the plane. If they approve the opinions of stuffed shirts who might feel otherwise are of no importance.

The same applies to cruises. There are those cruisers who want to relive their high school prom by stuffing themselves into tuxes and evening gowns on "formal night." As long as the maître d' doesn't deny me access to the main dining room then the aspirations of the fancy dressers to have everyone display the same degree of sartorial splendor will go unsatisfied. So far I've never been turned away and I don't wear a jacket and tie on holiday.