Laura Hudson at Wired explains the problem with the dearth of major, three-dimensional female characters in film, particularly sci-fi/fantasy film:
Criticisms about representations of gender (or race and other diversity) are often countered in fandom by sociological or scientific analyses attempting to explain why the inequality happens according to the internal logic of the fictional world. As though there is any real reason that anything happens in a story except that someone chose to write it that way.
Fiction is not Darwinian: It contains no impartial process of evolution that dispassionately produces the events of a fictional universe. Fiction is miraculously, fundamentally Creationist. When we make worlds, we become gods. And gods are responsible for the things they create, particularly when they create them in their own image.
As Tracy Jordan would say, “Tell it to me in Star Wars”.