The guys are wearing tuxes, which is a nice way to go if you can afford it, but that's not the most interesting thing. The really interesting thing is that they're all wearing black and white. When two black-suited men talk to each other they merge into a new black sillouette which incorporates them both. When a third or a fourth join them they form another shape still. A bunch of men alone still form a pattern: dalmation spots against a sea of white. As long as every man wears black the dark shapes keep changing all night like a kaliedescope.
Another reason a guy should wear black is that it sets off the girl he's with. If the girl wears light colors or flower patterns then black makes a perfect contrast (I can't believe how gay this sounds!). You would think that guys would lose their individuality by becomming a background for the women they're with. Oddly enough that isn't true. Black is background but it's also agressively foreground. Black and white looks good on a guy, they're's no denying it.