Who told you it requires both hand to use? Some apps do require both hands, but basic functions are handsfree. Time and alerts are handsfree. Want to see the time, raise your arm and look at the watch like you would any watch. Alerts turn it on and tap you on the wrist. If you decide it requires more, then you may need to take out your phone. The watch can operate independent of the iPhone for certain operations related to exercise such as running, walking, etc. It also responds to voice commands.
Sure not everything requires both hands. But for all the functionality it does require an iphone, and there will be many things that will require or will have an option thst people will decide to use, that needs the other hand.