I was thinking something similar the other day. I am sure I could quite happily go back to living without mine, but I do use it frequently for alot of things. The ability to text message is great for keeping in touch with my friends and vice versa. Also the number of times I have been ability just ,'show' an email at a shop, pub etc is helpful. It is my calculator, calender, clock, diary, phone book, map, route planner, check my bank balance etc, calorie counter, dictionary, organiser, and I use most of them daily. I used to use it for games, but I don't play anymore, I have gone back to reading more. I remember breaking down in a car at night before them and are grateful for them in that respect. I do have all my numbers, diary, lists and certain things handwritten down as a back up in case it broke, I learnt that one the hard way!
I don't judge anyone for not having one or what kind they have. Mine has enhanced the organisation of my life. But if I wanted to get away from it all and relax it would be ditched first.