[jack-r-abbit]

Maybe with their shirts undone to their waist

First off, those women don't have any thing undone. In fact, their shirts go all the way to the neck. No cleavage. One pic has one of the women showing a little (tiny, tiny) midriff but the image cropping really minimizes the amount of skin shown. They are dressed in a "fun take on the black tie affair" kind of way... not half nekkid. So your comparison on the men with shirts undone to their waist is quite a bit extreme.

sharing a kiss

Second, call it a crazy double standard or what have you but the fact is, many girl friends do stuff like this while not many guys do. When my wife is hanging out with her girl friends it is not uncommon for one of them to lick another at some point in the evening. I can honestly say that I don't recall ever being involved in a licking with another guy. I also don't accompany my guy friends to the restroom but that seems to be popular with the women. Men and women are different after all.