I am digging the recesses of the internet now to find out about Sadma/Moonram Pirai and why it is done that way. 😳
From a eulogy of Balu Mahendra
Relevant passage.
Shobha would become the first scandal in Balu's life. A torrid affair ensued. Even as Shobha went on to earn the National Award her personal life was on a slide. It is said that she would act like a truant child around 'uncle' Balu Mahendra. One day Shobha committed suicide and Balu was suspected as having played a role.
Balu would later tell in an interview "I was crucified'. That was unfair. Shobha was the victim not he. He added that stung by the controversy he vowed silence until after a year when he "threw down Moondram Pirai" as answer. Balu Mahendra brought to screen, with fantastic acting by Sri Devi, a platonic relationship between a nubile woman who, due to an accident loses her mind and is also amnesiac, acts childlike (not childish) and a young man who happens to meet her in a brothel but ends up rescuing her. Kamal Hasan earned a National Award for his heart rending performance in the famous climax. A third factor in the success of the movie was then sex goddess Silk Smitha. That even a sensitive filmmaker like Balu had to rely on the uninhibited oomph factor of Smitha made people chuckle at the commercial compromise. He later did accept the compromise but he added that Smitha's presence served a purpose. Kamal rebuffs Smitha's seduction and thus lends credence to the fact that he could have an asexual, sort of platonic, love with a nubile girl. Balu, sanitized his relationship with Shobha thanks to an artistic movie made with commercial compromises. Their relationship, to be sure, was anything but platonic or even the implied paternalism of 'Moondram Pirai'.
9