Selena Gomez had to learn how to smoke in order to properly act out her role in “Spring Breakers”. Anything Hollywood reports that Gomez had never smoked in her life before and she had to be shown how to do it.
As to why she accepted the role, Gomez replied that she had grown tired from doing the same roles over and over again. In addition to doing something completely different from what we're used to, Gomez stated she wants to be taken seriously as an actress.