There was not enough time to get to know all the great directors on Melissa's panel and also take on why they're so under-used. There's probably not enough time to address this complex issue in a blog post either, but let's give it a whirl:
"It's all about money": Everyone knows that the entertainment industry revolves around money, just like every other industry. (People in entertainment say "it's all about money" like this should come as some kind of surprise.) It's not possible to gage if films directed by women gross less than those directed by men simply because of the female-ness of a director; the films we'd be comparing would be different. Men overwhelmingly direct more action/adventure blockbusters than women and these have bigger profits. It's ironic that the highest grossing female director at the time of this writing is not a man, but she used to be. I don't know if many women are up for films in the action/adventure genres, but no one seems to want to take the risk in hiring them (a woman director is not a risk, being blamed for hiring one is). Enormous investments are at stake and a box-office failure could be blamed on the choice of a woman director, especially one with no track record in the genre. That said, I don't think I ever heard that a film flopped because the director was a man.
There's also the notion that men and women go to action/adventure blockbusters together, while women have to drag their husbands to the latest romantic comedy or family drama. Do "male-driven" films attract both men and women, whereas "female-driven" films attract women only, half of the possible audience? This is a gross generalization, but there may be something to it. Try to imagine how many men, on their own, might run out to see a film like Miranda July's Me And You And Everyone We Know, as great as it was.
"It's all about networking" - I wonder if fewer women are out drinking all night at events like Sundance and if this is when the foundations are laid for deal making (do I really have to wonder?). Booking pole dancers for a party might be fun, but it is probably not as comfortable for the women in the room whether they'd like to admit it or not. At Cannes I noticed lots of men of a certain age were happy to chat about films during the day, but in the evenings they travel in cliques and entertain young women who could be described as "teenage." So networking opportunities for women may be more limited not because of gender, but because of actual sex. If the entertainment industry is all about money, sex is the close second.
"It's all about status" - Right now, men still control most of the decision making and financing in Hollywood. Is it possible that, aside from the perceived financial risk and limited camaraderie, there's just something emasculating about choosing a woman director that's hard to pin down?
I suspect many executives are unconscious of these tendencies, but this culture will probably continue until women regularly rake in huge box office numbers and climb to higher positions in the executive ranks. It is encouraging to know that when women have the power, they do hire and support other women, according to this study by the Sundance Institute.
Meanwhile, check out Melissa's book for fun and inspiration.