It provides real functionality because it frees you from your phone. If you have a smartwatch, you spend less time looking at notifications, period. Looking at your phone for things takes a few seconds at a minimum. With a watch it takes just a glance. Same when it comes to replying to some messages. The difference is small, but the impact can be big.

It is liberating in a way. If you check your phone 20+ times a day, you notice the difference.