Interacting with a device on your wrist requires you to use the other hand.
I've seen a few experiments where devices on the wrist can detect responses to notifications on the wrist by specific gestures and movements with the hand but nothing that can let me browse content or initialize an action. While I expect lots of people to end up experimenting with this in future, I'm not expecting anything amazing any time soon.
The device in my pocket? I can take that out and use it (well the vast majority of functionality) with just one hand.
This matters because there are often times when it's not always possible to use both hands. Sometimes it's just more convenient to only use one.
Yes, some interesting things are happening, and will continue to happen, with wrist worn computers. Just don't expect them to replace the ones in your pocket for quite a while yet.