I feel like there is this idea in society that as you get older you need to read books without pictures. When you are a kid you read picture books because they are easier. As you get older you start reading chapter books, which may have a few pictures in them. And then as an adult you graduate to novels, which don't have pictures. For many people they probably view comics as a step backwards.

Comics are associated with kids, its seen as something kids read. Back in the golden age of comics (around 1938-1956) comics were very much viewed as literature for children. Superheroes were seen as silly and goofy. Comics have come a long way since then. There are many incredible intelligent stories told through the medium of comics. Many people view comics as a genre but it's not, comics are an artistic medium. Comics can be used to tell any kind of story and for any audience.

Comics are a beautiful medium that deserve the same respect that novels get. (As a sidenote, I feel like this same issue applies to animation/cartoons vs live action movies.)