The classroom is an excellent place to practice good communication skills. Instructors should be covering things that are not in the textbook. Not coming to class is disrespectful. Expressing thoughts aloud during class discussion helps students learn. Students cannot learn what's taught in class if they are not there.
Class provides development beyond the text.
Communicating with colleagues is learning. If instructors allow absences, the message is that what is done in class is not important. Student attendance allows the instructor to determine what students gained from assigned readings. Students are adults who need to make their own choices. Our students have tremendous obligations.