Actually, casual sex in many ways is better for women than committed sex. Just like a lot of other stuff surrounding sex and relationships, the recieved wisdom is not necessarily true and might actually be another tool of the patriarchy.
Because women who are encouraged to 'save' sex for relationships are women who are going to have to wash the bloke's shitty pants and cook his dinner and stroke his ego as well as having sex with him. And prioritising The Relationship often means having sex you don't really want, with a bloke who isn't very good at it, because you 'love' him and therefore it's all about keeping him happy.
Whereas if you have sex with a bloke you just met, or only see from time to time, you don't have to do his housework or listen to long rambles about how his day at work went, and if he isn't any fun you can just bin him and move on.