Fast Access to Important Actions
You no longer need to tap reply to reply to a message on Apple Watch. The options to reply are right there so that you can tap them to send a message back immediately instead of tapping and tapping again.
This is just one of the changes to Apple Watch apps. Apple spent time redesigning the core Apple Watch apps so that you can take action without tapping again and again.
Another example is the Quick Start Workout option that lets you jump right into the workout you want to do without waiting for the app to load and then scrolling through options.