In India, both Bollywood and Hollywood movies are released in cinema hall only on Friday. What is the reason?
What I think is that because after Friday you have two days of weekend holiday (Saturday and Sunday) to enjoy the movie.
The same question was asked to The Times of India and the answer by Jayant Mukherjee was: (emphasis added)
The release of films in India follows the American style. There a film is released on Friday so that people can watch the film with their family during the work-free weekends (Saturday and Sunday) leading to good opening collection.
So it's not an India-only thing, we picked up this method from western countries.
However, the trend of releasing movies on a Friday didn't start in India until the late 1950s. Neel Kamal released on 24th March, 1947, which was a Monday. Mughal-E-Azam was among the first movies to be released on 5th August, 1960, a Friday. So we ended up adopting the British/American legacy after all, in the late 1950s.
Also, Friday is considered as the day of goddess Lakshmi in India. So, releasing movies on Friday came from the belief that producers would be blessed with good wealth.