From a business point of view, cinemas are only partly about films. "When we bought [Odeon]," Guy Hands of private equity group Terra Firma famously said, "the management team really believed they were part of the film business. I had the difficult job of explaining to them that they were in the popcorn-selling business." (Oliver Thring, Guardian 2012)
That hideous diabetes/clot-encouraging popcorn is set to become the main revenue stream for cinemas - movies could become a loss-leader, just as budget airlines seek to make money from flight 'extras' and in-flight sales more than the actual seat purchase - very bad news for distributors.
That process is arguably already here though...
The pic above is from a Guardian article on an American cinema-goer launching a doomed lawsuit against the US cinema chain for charging $8 for a coke. From the same article: