I think all the professors who are banning laptops from their classrooms read Jurassic Park. The movie is excellent; the book is even better. Way back in 1990, Michael Crichton wrote:
In the information society, nobody thinks. We expected to banish paper, but we actually banished thought.
Back then, people probably thought he was an alarmist. Maybe some people still do. "Laptops help you think by putting information at your fingertips!" Or maybe they just help you take down every single word the professor says, which is way too much information to be helpful.
Or, and I'm walking out on a limb here, maybe you just want to chat with your friends and check your email.