I often have only one hand or no hands free - I'm carrying a child/large objects/sacks of groceries - and I need to be paying attention to the current situation and my surroundings, not a small animated display. With the Pebble, I had a smartwatch that was usable entirely through learned muscle memory, e.g., "I don't know who's calling me right now, but I am not able to take the call, short press on the bottom button to decline and dump to voice mail."