Women constitute about half of the human population. It is not clear when exactly the subjugation of the other gender seemed like a plausible prospect to men. As it happened, at some point in our history, men managed to keep a tight rein on women and have been doing it to this day. Patriarchy has always been a deep-seated notion in societies all over the world. Even today, relatively few women have the liberty to make decisions of their own accord. At large, it's the men closely related to a woman who call the shots regarding her life.
Given this reality, it shouldn't actually be surprising that women are often relegated to secondary roles in the majority of films. An objective portrayal of women is seldom seen in mainstream cinema. Since the preponderance of the mainstream films are produced and conceptualized by men, the female characters are often viewed through the 'male gaze' (a term coined by the film critic Laura Mulvey). Women are shown on screen from the perspective of, in most cases, a heterosexual man. More often than not, in mainstream films, the ideal woman is depicted as the one who is content with playing second fiddle to her male partner – the one who is too happy to sacrifice her dreams and ambitions for him, the one who bears with all his misdemeanors without daring to question them, the one who accepts infidelity on his part as an inherent trait of manhood and forgives it, and so forth. Any female character who doesn't conform to these rules is readily denounced as being brash and undignified. An ambitious man is often depicted as being worthy of praise whereas a woman with the same trait is hardly ever shown in a positive light. Such a woman is often shown as being remiss in her duties as a mother or wife. It goes without saying that this character often eats humble pie towards the end of the story and realizes how 'wrong' she was in desiring something apart from a family life. Also, it's almost impossible to find a scene in mainstream films wherein the topic of the conversation between two (or more) female characters is something other than a man. The female characters often have nothing going on in their lives other than their thoughts about a man.
This is not to say that independent female characters don't exist at all; they do, but they are few and far between. They are so rare that whenever a film's protagonist is a woman, people get preoccupied with that fact and refuse to treat the film as a thriller, fantasy, comedy, or a whodunit. The film is readily filed under the genre 'woman-centric'.
Another disturbing trend in cinema is the romanticization of stalking. As per section 354D in the Indian Penal Code, stalking is an offense that can be penalized with up to three years of imprisonment. Nevertheless, since time immemorial, stalking has been depicted in cinema as the most efficacious avenue of winning a woman's heart, an essential part of courtship. The message given out is this: a woman, in spite of putting on an outward protest when being stalked, secretly enjoys being chased, and that when she says 'no', it isn't actually 'no', but 'yes' in disguise. This exercise becomes all the more pernicious when the stalker is played by a superstar who is looked up to by legions of impressionable youth. Then again, such films almost never regard the hero as a stalker. He is depicted as a hopeless Romeo who is so much in love with the lady that he has zero respect for her choices and decisions.
And as far as actresses, especially those who play leading roles, are concerned, they have to deal with what their male counterparts don't: shelf life. Very few actresses have been fortunate enough to continue acting, let alone play the leading role, post their marriage. Upon getting married, they are expected to give up their career in cinema and be a good homemaker. Those lucky ones who keep at it even after their nuptials barely ever get to play the leading roles again. They are invariably handed down the roles of the hero's mother or sister, characters that are often inconsequential to the plot. In many cases, the curtain is brought down on a female actor's career before they can explore and hone their craft further.
Many of the problematic conventions in cinematic storytelling regarding the depiction of women can be resolved only if educated, well-read women become part of the creative process of a film. Any substantial change in the status quo is virtually impossible without the support and solidarity of the men in the industry, especially the stalwarts who hold all the aces. One can only keep their fingers crossed and hope that a level playing field will materialize quite soon.