You know, it used to be that there were no formal nights on cruises. There was no need for that distinction since every night was white-tie, tails and top hat.
I think the modern proliferation of dining wear regulations has actually made the situation more complicated. More complicated than it used to be, and more complicated than it should be.
A gentleman would bring along his dinner wear, and that was it. No need to decide what to wear, no need to figure out regulations.
But to the question at hand: yes, I would miss Formal Nights if they were abolished. Another element of the elegance of cruising would fall away.
I guess I like traditions!