well i notice that too... here is my hypothesis.. hehe an educated guess...
- they chitchat and ask each others opinion about something they want to talk privately... (why of all places the toilet?)
- they feel the common urge of needing the toilet
- they ask each others opinion about their appearance
- they simple want to have someone to talk to or they want company....
- they are too dependent to go to the toilet alone (too much parently love?)
- and my last guess is that they are afraid that whatever happens in the horror movies they watch (such as, a white lady coming from the ceiling, blood coming from everywhere and etc.) might happen to them.

and about your second question....
yes, they talk about men in there but not all the times... hehehehe.......

Source: http://answers.yahoo.com/question/index?qid=20080204034102AA5ENZ5