Yeah, vanity is definitely involved. But it definitely proves practical a lot of times. It's just one of those rites of passage when riding fixed, I guess.
With clips and clipless pedals alike, I just find it a lot faster to trackstand for a bit, then jump the light or make my turn, rather than trying to scramble back into your clips or to clip in. I mean, I'm sure it's not that big of a deal getting into your pedals, I just think it's faster.
usually when it's a long light, it's not worth the effort to stay on your bike the entire time. my 2 cents.
But yes, I've seen roadies to it too.