Why Apple would do an iWatch?

1. Wearable computing devices are the next step in consumer electronics. 
2. An iWatch product line would add value to the iOS ecosystem (iPad, iPhone, iPod touch) by offering features that only makes sense on a smart watch and complement our iDevices. One example: proximity sensors that would suppress the need for passcode on our iDevices when both are close each other.
3. Because Apple can. They have everything they need in order to do it: complete control of their stack (iOS, hardware, service, sales), miniaturization expertise, best design team, lots of potential buyers (all those already using an iDevice), powerful processor, sharp focus on user experience and market opportunities.