It has to do with separate rights for movies for each distribution type. Managed competition for each market.
The standard release routine for a movie is regulated by a business model called "release windows". The release windows system was first conceived in the early '80s, on the brink of the home entertainment market, as a strategy to keep different instances of a movie from competing with each other, allowing the movie to take advantage of different markets (cinema, home video, TV, etc.) at different times.
In the standard drill, a movie is first released through movie theaters (theatrical window), then, after approximately 16 and a half weeks, it is released to DVD (entering its video window). After an additional number of months it is released to Pay TV and VOD services and approximately two years after its theatrical release date, it is made available for free-to-air TV