The white tuxedo is always a symbol of class. Players don't often think about the specifics of clothing in games, but it plays a big role in social expectations and interactions in real life, so it makes sense that it should in a campaign world too.
If you establish that the majority of people typically wear grubby, rumpled, homespun stuff in a dozen exciting shades of brown, then the simple act of describing a person wearing immaculate clothing in crisp, neatly tailored lines with vibrant hues of sky blue and pale yellow instantly makes them stand out from the crowd and conveys that this is someone important.
aurilee writes:
Commentary by memnarch (who has not seen the movie)
Ooooooh dear. Hey Ben, here's the perfect opportunity to top Jim's plan improv! Finn's even getting the white glove treatment! Oh, sorry; I just noticed Rose is falling over in the last panel too.
Anyway, it took the patrons long enough to notice the problem with the outfits. It's extremely amusing that Finn points someone out, or something out, just before immediately getting spotted for that. There's probably some other reason Finn and Rose are getting called out, like Finn getting called out for being First Order again, but imagine if the clothing is actually the main reason!
Weapons though? I don't think I spotted any weapons so far. Maybe Finn's got a blaster on him in the third panel, but it's hard to tell for sure. No droids makes sense at least. A casino wouldn't want anyone to be able to tell the odds of winning too easily, and a droid can probably hack things faster than a biological person can.