I stopped wearing a watch as soon as I had a phone with a clock.
I resumed wearing a watch as soon as I heard of the Basis fitness watch. It tracks heart rate, skin temp, perspiration, and movement. Unfortunately they chose to not include alarm functionality, so I wear a Fitbit next to the watch. I really like the silent alarm functionality on the Fitbit.
on topic:
A smart watch should do what the Basis does, it should also feature vibration alarm, visual notifications of incoming calls, messages, and social media with the notifications highly configurable by the user.
I think a watch with all these features would convince many people to start wearing a watch again.