the way I see it is:
every woman is different. There are women who are more masculine that have adapted or at least 'try to adapt' men's qualities and so they will be more open to casual sex.
some women have low self esteem and so they will give a man casual sex hoping that after she gives him sex he will want her for a serious relationship.
some women are more sensitive and get attached easily so they will never go for casual sex without a commitment.
The geography factor also plays some role here. Women are known to adapt to their environment more than men. So if you live in a city where most Women are sexualy open- most chances are you will find many women that will be fine with casual sex.
Women in Jari's area in Finland are very sexualy open, Also French Canadian girls in some parts of Canada are the same (David X was having a ball with French Canadian girls)
I think that in Montreal\Canada there are also a lot of sexualy liberated women (David X used to operate there a lot as well

).