I guess if you've bought the ticket then fair enough, probably I'm an old fart but doesn't anyone make an effort these days?
In the days when I travelled regularly on ID fares I had to comply with some pretty strict dress codes. It was worth it because (in those good old days) non-rev would often be upgraded to Business or First. What I found amusing is that much of the time it was pretty easy to distinguish rev from non-rev as the non-rev were often the better dressed
Now days I pay my own tickets in Business and I enjoy dressing casually, although not in vests or flip-flops I must stress.