I think some clubs that claim to have a "dress code" are actually just trying to enforce a "no trash customers" code but need to put it more politically correctly than that. Until about 2015 or so, French Quarter clubs in NOLa on weekends used to generally reject people wearing blue jeans and t-shirts, except maybe big groups of matching t-shirts for bachelor parties, since the crowds pouring in and out from Bourbon Street aren't necessarily dedicated strip-club goers, so they were simply trying to put some kind of control on the door. But recently they'll take whatever they can get.
For another example, the report from TheeOSU about getting kicked from an otherwise empty club for wearing a bandana suggests to me NOT that the manager / owner was trying to be upscale, but rather that he was looking for high-paying customers who wouldn't cause him grief. The original post admits, directly, "this was back in our young days when neither one of us were aware." Probably got kicked for having that appearance, not just for the bandana, is my guess. If you'd been a regular you'd have known something -- maybe the crowd was scheduled to arrive later? Maybe the "dancers" were all direct-to-the-service hookers and there wasn't much dancing at all? College kids in sweatshirts and bandanas aren't usually wanted in places like that.
As to sweatpants ... I used to regularly monger in a pair of pants that came from a super-silk style track suit. Very smooth, almost velour type, but slick on the outside like a wind-breaker. Dancers loved them, it was like pajamas or a micro-fiber blanket. But I started to feel like they were creepy-looking, since they were clinging to my thighs and bulge. So I ended up researching (here at TUSCL!) good slacks and upgraded (Hagar Cool 18s). At a club I recently saw a kid in sweatpants with a dress shirt and cross-trainers, he looked too incongruous, it was like he hadn't finished putting on his costume for the school play. He was tall and his semi-boner was poking through the pants too obviously when he went out to the patio (it's more brightly lighted) for a smoke. We didn't appreciate it. "We" means me, all the dancers, and anybody else who mattered.