I never understood why people say "I don't need a watch, I have a phone in my pocket!" You know why watches were invented, right? Personally I've been thinking about getting a pager.
With a watch, I can read the time in 1/10 of a second, I don't have to dig it out of my pocket and turn it on, I can surreptitiously check the time, I can read it without my glasses on, I can read it out of the corner of my eye, it doesn't bounce around annoyingly in my pocket when I jog, it lasts a year on a charge, it works on an airplane, I can read it when my hands are full, I can check the time without taking my hands off the steering wheel, it works in the rain, etc.
The only thing I don't like about a watch is I have to remember to take it off when working with rotating machinery.
Besides the advantages others listed, I simply like the smaller size of it. It fits in my pocket without being annoying.
I also wear a wristwatch. Gosh, I'm old!