Because women were objectified in (almost all ) films until recently and ogling a married woman on screen may not have be an exciting idea for the repressed male audiences until Savita Bhabhi showed up and introduced them to a new line of thinking. Commerical success usually came from naach gana films and they were all made by men, for men. Actresses were mostly used as eye candy /m#sturb#tion material . There were no lead roles for women above 35. When you were too old to run around trees or thrust provocatively at the camera you were shunned and a younger woman, young enough to be the male stars' daughter was chosen instead. I'm glad that women oriented roles for actresses above that threshold are being written these days. Without it being called 'parallel cinema'.
Kangana's video with AIB pretty much sums it up
Another reason could be the insecurity of the outwardly progressive husbands . " I don't like it when you are being hugged and touched by other guys even if it's on camera " .
Let's face it..it's hard to sell author backed stories about women above a certain age because our society can't stand the fact that women live interesting entertaining lives after college. Even in the case of films about younger women..take Chal De India for example; if they hadn't cast SRK as the coach it wouldn't have seen daylight.
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