Students find it unlikely that a professor will remember their faces, or that they will be recognized as the single most rude student in a lecture hall of 300 people. I have found that students in my upper-division classes are less rude in lecture. This may be because the class size is generally smaller, but perhaps it is also because students do care about the material that they are learning about. The indifference most of us feel toward our mandatory general education classes during our first years in college may account for some disrespectful treatment of professors. It is also more likely that students in upper division classes are more interested in pursuing a professional relationship with the professor as graduate school application due dates get closer, and it becomes important to make favorable impressions.
Students also disrespect the lecture halls themselves.
I am disappointed to see initials engraved into desks or profanity scrawled on the backs of chairs. Part of being respectful to others is keeping your area clean, not to mention working to preserve the rooms for future Bruins. We are recognized by both the law and each other as adults, and yet the immaturity of grafitti and gumwads seem to speak otherwise. Perhaps the behavior of students in lecture is really the sign of a larger problem. Maybe students feel obligated to come to college because of their parents, or feel that the only way they'll be successful is to major in something they hate and get a job doing something they equally hate.