The aesthetic value of both literary and cinematographic works ranges from superficial entertainment to highly complex masterpieces, but the language has a special term art films for the films that are striving to be at the higher end of that scale, and no analogous term, such as art literature, for the comparable literary works. Why?
The answer is that the terms film and literature are anchored in the different parts of the scale of aesthetic merit. When one hears the terms film or movies, without any qualification, one is likely to think first of the typical products of the Hollywood studios. These are the films that are designed to be as commercially profitable as possible, by being entertaining and appealing to wide audiences, and that do not even attempt to achieve any artistic value that might get in the way of commercial success. Because this is the default for the concept of a film, we need a special term for the films that depart from the default, and art film, in some contexts, serves that purpose. On the other hand, the term literature is, for most people, anchored in the classics that they read as a part of their education. When they hear the word literature they first think of such works, which are of relatively high artistic value. We thus do not need any qualifier to add to literature in order to direct attention to the higher end of the scale of artistic merit, because the word literature does that by itself. In the case of literature, we do, however, need special terms, such as pulp fiction for the works at the lower end of the scale.
(This answer elaborates on what was first posted by FumbleFingers in a comment.)