Watches are also a piece of jewelry and a statement of personal style. There are appropriate watches for certain occasions. Most people wouldn’t wear an iwatch to a job interview or black-tie event.
The thing is pretty bulky too - I can easily see scratching the display as it brushes against everyday stuff.
I heard much of the same reasoning when cell phones first arrived: to wit “wired phones are perfectly functional, most people wouldn’t want to carry a phone around with them all the time (especially a job interview or black-tie event); cell phones are pretty bulky too, I can see breaking one pretty easily in everyday situations.”