As one of the very few urbanites left on this planet without a cell phone, I can honestly say, I heart being unplugged and unavailable.
Of course, I can still be dialed-up the old fashioned way via land line--suits me just fine.
By not using a cell phone, I'm not only saving money, I may be doing myself a health favor, avoiding the very real risk of stimulating cancer cells.
Keys, glasses, water.
That's all I need when I walk out the door. At the rate I misplace my glasses, I really can't afford one more thing to keep track of or lose.