Why there are "Race Movies"

Per our discussion on The Best Man Holliday, our professor posed a really intriguing question that has been puzzling me for the past couple of days, and that is why movies like Django Unchained, 12 Years a Slave, and even The Butler have been framed as being movies for all audiences (Black, White, Hispanic, Asian, etc), and have been very hyped up by the media stating that people of all audiences needs to see these movies, while movies like The Best Man Holliday, Tyler Perry's movies, and the like, even though those movies can be labeled as comedies, are now being labeled as "Black Comedies," or "Race Themed" movies. Then I thought of the way the first types of movies were being put out there by the media, with Django being promoted by Quentin Tarantino, it was framed as almost looking like a cowboy movie with the emphis of being "fictional," even though we know some of the things that happened in that movie actually happened in history. Looking at 12 Years, and The Butler, both of those movies were very much promoted by Oprah, who is a big media figure for all audiences (meaning they watched those movies because again, she speaks to all types of audiences, so it's not looked at like a "race movie," but a movie that everyone can look at. While the other kinds of movies are not being exposed like that to all audiences, but only to Black people, which is why people would say that it's a "race themed movie,"