Is Reading background Subtitles....

Is reading background subtitles or subtitles that don't need reading worth it? When watching anime, there are subtitles that are in background (people walking streets, school halls, or anything you can imagine) where the subtitle show, when main character talking/thinking. Then you have a teacher speaking giving a lecture, at the same time a main character thinking. For me, I can't really say yes or no to this one. I basically read every subtitle that is showing. So what is your thought on this?