Films are sold on star image. They are not just labour but they are a form of capital too because they create an advantage for the film that it would not have if it just had an ordinary actor in the role, so they will hopefully get good profits.
Not all film actors are stars though. Stars have to do extra publicity for films, interviews and premieres and do not usually have to audition for parts. Ordinary actors will have to audition and do not usually have to do the publicity which stars do. They do not get the glamour of being a star. …