I agree with the comments about people being lonely without the reassurance of speaking to someone or just hearing something in their ears. No one in Singapore for instance seems comfortable on any public transport unless they have something in their ears, or they are jabbering on the phone, or stroking their bl**dy iPhone. No one is happy just to sit with their own thoughts - maybe they don't have any?
When flying, I turn the phone and BB off when I leave the lounge, and don't switch them back on until I am off the plane and ready to deal with whatever's there. I am bombarded with calls and questions all day so the period of peace on the plane is really, really pleasant. I know I am quite important, and I don't feel the need to show other people how important I am.