There was also a degree of respect for the audience. It was assumed that the people in the theater could use their imagination. They did not need a 20-minute sex scene to know that Bogart and Bergman were having a physical relationship. The audience was treated like adults, rather than teenagers. Hollywood often relied on high-brow culture in their films, even though their audience was mostly working class. People read more and they were expected to know about classic stories and characters from Western culture.
Source: The Olden Thymes | The Z Blog