It reminds me of teachers' and professors' attitude towards their classes/courses. From their point of view, it's maybe the only thing they teach or one of 2-3 things and it's the general topic they spend all their time on. From a student's perspective it's one of many courses in various topics. They can't be expected to laser focus on just the class that you teach. But many teachers don't get this concept. They think everything revolves around their course only.