I use a wristwatch, and I'm 19!
I like it for 3 reasons:
1) I can wear it when I run and work out. Having a cellphone in your pocket while running is a great way to lose/damage your phone.
2) mine is water proof. I can wear it in the pool, diving, or in the rain. good luck bringing your cellphone to the pool or scuba-diving.
3) I can always tell the time. Cell Phones have battery life that is basically universally less than one week. My wrist watch is 2 years old and still keeps the time perfectly.
edit: oh, everyone wondering, my watch cost $20, has the date, day of week, 2 clocks, a stopwatch, and an alarm and is water-proof to 330 feet.
Mine is purely practical, I don't understand the train of thought that watches are ONLY for fashion.