Movie adaptation comics seemed a little odd to me, since they give away the whole plot and ending, which might reduce the potential audience for the film in cinemas. This practice dates back to radio as well, with the Lux Radio Theatre running from 1934-1955 and a TV version from 1954-57 (before that the television show was only 30 minutes and didn't adapt pre-existing films). The comics based on TV shows didn't face the same problem, since they presented "new adventures" of TV characters.
Link to the book:
Hollywood Film Stories 2