On the odd occasion mrs thing and I feel flush enough to travel business we make a bit of an effort. Chinos, a decent shirt and shoes for me and whatever the female equivalent is. We were boarding a SIA 380 recently and a guy turned off the boarding ramp into suites wearing cut off denim shorts, a vest (and I mean a vest, not a t-shirt) and a pair of flip flops...
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?