@robert - Loved your comment, but had quite a good chuckle for some time, just seeing that picture...Oh, man that is funny! It is just because it is something society is not used to. Say like: Women with unshaven legs perhaps, but men are fine either way. Women can wear dresses and pants....men, not so much. Back to the question:
I think it is a wild expression of:"I want you hot stuff!" but these girls know there are competition, so I wonder if some of them buy like a whole pack of underware or if some write their names and numbers on the labels.(might be a bit small) Or you are actually a xxxxL size, but you throw S-sizes on the stage? I don't know really, because if it was all about competition, I recon some would just throw their whole wardrobe on the stage or (because the way to a man's heart is through his stomach) they might just start throwing tasty recipies on stage to impress them with their cooking talent.
Yeah...so now I am really confuced - there is absolutly no explination for this behaviour.
I'm sure there must be some woman out there that can answer this.