Cellphone, especially smartphone, is very useful. Not only for entertainment, some people use smartphone to do their job. Addiction is bad but maybe in some cases it's not addiction, people actually need the smartphone to accomplish something. If I leave home without my smartphone, yes I would feel that I'm missing something. But I don't think it's because I'm addicted to my phone, it's just a pretty handy thing to have. Your family or somebody can reach you anytime anywhere, or when you have trouble you could call someone to ask for help, etc.