Don't know why, just bugs me to wear them, and I keep bashing them on things. Before I got a cell phone, I wore a carabiner watch on my belt and it was pretty cool...they were built with cheap springs though, had a tendency to stop staying clipped after a year or two, and after I lost one down an elevator shaft while disembarking I pretty much swore off timepieces (coincidentally that's around when I got a cell phone and stopped needing them).
I guess if I was working in a physical, mobile job...where taking a phone out was inconvenient (dirty hands, gloves, hands always full)...and being able to time things was really important...I'd wear a watch. I could control it with voice, that could be a killer app for some job I don't know what. ("Smartwatch, give me a thirty second countdown on my mark... Mark.") Yeah, the only use for a watch in my mind is checking the time without using your pockets, and always-on voice control is the only "smart" addition that makes sense. If you had the use of your hands to fumble with buttons or a touch screen, a phone would be easier to use.