The trick is that the phone is a lousy device for consuming notifications. You're either tying up your hand holding it or it's sitting in your pocket and not actually helping. Comparatively, the watch can pass notifications while leaving your hands free, allowing you to get things done.
In the sordid tradition of technology prognosticators, I'm going to make a prediction: there will never be a strong game market for the smartwatch like there was for the smartphone. Games work on the phone because the phone is what you stare at when you're bored. The smartwatch isn't for when you're bored, but rather for when you're busy, so there's no point in gaming on it.
I'll second this, but I think there is possibly a huge market for the watch/healthkit integration. As a runner, I'm really excited about the possibilities of a customizable tracker that I don't have to carry in my hand while I run. Particularly pacing my runs. I'd love to have the adaptive touch let me know when I'm falling out of a set pace.
In the sordid tradition of technology prognosticators, I'm going to make a prediction: there will never be a strong game market for the smartwatch like there was for the smartphone. Games work on the phone because the phone is what you stare at when you're bored. The smartwatch isn't for when you're bored, but rather for when you're busy, so there's no point in gaming on it.