Don't see what the big deal is with the workout clothes. I've worn the same t-shirt twice in the same week the odd occasion, sometimes you just forget to throw a fresh one in your gym bag.
What does bother me is seeing people work out in jeans, or big fucking boots, shirts with the collars popped, and worst of all a toque (that's a beanie to you yankees). Why the fuck would you wear a toque in the gym? Nobody thinks you look extra badass doing chest/bis in your toque 3 days a week.
One of the funnier gym attire moments was about a month ago this guy was basically walking up and down the gym and chatting with people but the funny part was his hat was slowly rotating around his head. Started off tilted forward right, then straight right, then back right, then totally backwars, then back left, then full left, then left front. I don't think i saw him do so much as lift a dumbell, just walk around the gym getting in peoples way while his hat was gradually going clockwise.