Why teachers in literature discourage students from reading comics which can be read in pocketbooks?

The goal of English teachers is to expose students to texts they may not ordinarily come in contact with. Literature opens up a world of various cultures and social levels, both past and present. Literature encourages the reader to think about universal themes which speak to all level of peoples of all times. People usually favor texts that are within their comfort zone which means they may not be challenged to think beyond their immediate level. Comics are fine for relaxation and downtime, or when a person needs a simplification due to low reading comprehension.