Back in the day, things like these were outlawed and the government tried to ensure competition in the markets:
> The major film studios owned the theaters where their motion pictures were shown, either in partnerships or outright. Thus, specific theater chains showed only the films produced by the studio that owned them. The studios created the films, had the writers, directors, producers and actors on staff (under contract), owned the film processing and laboratories, created the prints and distributed them through the theaters that they owned: In other words, the studios were vertically integrated, creating a de facto oligopoly. [...] Ultimately, this issue of the studios' then-alleged (and later upheld) illegal trade practices led to all the major movie studios being sued in 1938 by the U.S. Department of Justice.
> The major film studios owned the theaters where their motion pictures were shown, either in partnerships or outright. Thus, specific theater chains showed only the films produced by the studio that owned them. The studios created the films, had the writers, directors, producers and actors on staff (under contract), owned the film processing and laboratories, created the prints and distributed them through the theaters that they owned: In other words, the studios were vertically integrated, creating a de facto oligopoly. [...] Ultimately, this issue of the studios' then-alleged (and later upheld) illegal trade practices led to all the major movie studios being sued in 1938 by the U.S. Department of Justice.
https://en.wikipedia.org/wiki/United_States_v._Paramount_Pic....
Nowadays it seems like "vertically integrated" is something most companies openly aim for.