In my personal opinion, the lack of strong female friendships in women is down to 2 things:
- most women in literature, whether we like it or not, (and has been mentioned previously) are there to get the guy. Therefore, the other women are rivals. Sad as it is, if no female character has a clear love story they're usually portrayed as unfeminine and uninteresting. Why is this? Harks back to women and babies. Essentially, it's what we're for, and it's going to take a long time to change it.
- women are expected to be emotional. With men's friendship's there is almost always a hint of frisson, the forbidden, that these two men are unnaturally close, they'd do anything for each other, flirting with homosexuality. Since men are percieved to lack emotions - I'm hugely generalising, of course - or at least in comparison to women, their friendships seem more important. Women are expected to have loads of friends, and therefore it devalues the relationships.
On the female friends/kids debate, neither I nor any of my close friends have kids - I am only twenty, though - but I have plenty of female friends, though they change. I find it quite easy to flit between friends, and it doesn't bother me terribly when a friendship breaks down. Guys are easier to bond with because I can speak football, and after they get over the initial shock of it, it's a good starting point. Yet I have to say, in my experience, it's difficult to have a close female-male relationship that's purely platonic. I can't think of any off the top of my head in fiction, either. (Though bear with me, it's early...)
I do imagine, however, that I'll lose touch quite quickly with one of my better friends when she graduates university and no doubt marries her long-term bf and has children, and that saddens me. (Pop me in the anti-kids camp too, Mouse).