Filmi Music is the staple of the Indian music industry. Virtually every pop song in India is generated via filmi music, such that the entire genre itself is inextricably linked to this. Basically, every pop singer in India has been a playback singer in Bollywood, and the only way they can earn money is through the sale of songs via the sale of movie soundtracks. Filmi music is so dominant, that despite several attempts by various artists in The '80s, 90s, and early 2000s at creating a separate Indian ('Indi') Pop genre distinct from Bollywood, Indians still overwhelmingly listen to Bollywood movie soundtracks rather than individual pop singers or bands. Therefore, pop singers in India, while having their own respective fan followings, remain dependent on Bollywood studios for publicity, fame, and success, and pop singers do not have the stardom that other pop singers have in the Western world or East Asia.
One reason for this is that from its inception, modern-day Indian pop music did not have an independent avenue to thrive, unlike the case in the West. While in the West, modern pop music took off with the radio in the early 20th century, which enabled pop singers and musicians to broadcast their talent to a wide audience base, in India, government control over radio prevented pop singers from taking advantage of this medium. Government control over the radio originated in the British Raj, which only broadcast the news, western entertainment, or colonial propaganda. The Raj had a paternalistic approach towards the radio, treating it as a privilege of the British that shouldn’t be 'misused' by Indian nationalists. They would, therefore, deny Indian singers from broadcasting their songs, lest they incite 'disaffection against the British'. This paternalistic approach towards radio broadcasting continued in the early decades of newly Independent India, although for different reasons - it was felt that the radio should broadcast only classical Indian music, instead of low culture pop music, as a way of promoting Indian culture after years of colonial rule. Therefore, Indian singers, unlike Frank Sinatra and Edith Pfiaff, could not rely on the radio to develop their own fan base. An independent (of Bollywood) pop music scene did take hold briefly in the late eighties and early nineties, but died out by the turn of the millennium, with many of its artists being subsumed in Bollywood.
On the other hand, they could sing for Bollywood productions, which invariably had musical numbers or song and dance sequences once sound was adopted by filmmakers in India. Some of these singers, like Kishore Kumar, could sing and act in films, but eventually, they became playback singers. One reason may have been the fact that many singers, especially female ones, were classically trained vocalists, who had been discouraged from acting or dancing (classical music makes a clear distinction between singers, musicians, and dancers, and classical musicians had traditionally looked down upon acting and theatre as demeaning ventures), such that they lacked either the ability or inclination to sing or dance, which was a requirement for any musical. Besides, it was a convenient arrangement for actors, who usually came from various backgrounds in the early days of Bollywood, and lacked singing abilities (although many actresses were expected to have a dancing ability).
