I'm probably the most easy going, laid back type of guy anyone would ever want to meet.
Most workplaces have become casual wear. The only places I ever wear suit and tie are funerals and the occasional big formal weddings.
When you see movies of cruises, Loveboat etc., it seems like a tradition to have to wear a semblance of formal wear. Not necessarily tuxidoes but at least a suit or a navy blue blazer with tie. We have been on only 4 cruises, but we do enjoy having to dress semi formal a couple of times.
Would it bother me if there were no formal nights? No, not that much, but I would prefer a couple nights per week with a of a bit of formalities. It does add to the glamour of cruising.
There are so few times that semi formal wear is required and since it's like a tradition on cruises, I like it that way.