I have no doubt that one day we'll be able to have smartphones in the form of a smartwatch (I dunno, maybe with some sort of expandable holographic screen? - whatever sci-fi movie/show version you can think of), but for now, there's pretty much no need for it.
The article uses smartphones and tablets as the premise for the need for the smartwatch. This doesn't really work and won't work for a while until smartwatches can do everything a smartphone can do - without having to need a smartphone - and also not have to be charged for at least a day, if not a few days. Taking off your watch to charge it in the middle of the day sounds pretty dumb.
The smartphone solved multiple issues. You could now communicate through email and other social media forms on the go. You could access new, information, email, etc on the go (pretty much anywhere you wanted). You could have mobile entertainment. You could keep track of finances, school work, to-do lists, etc. You could do all of that in one little package.
A tablet emulated the same functions and solved the issue of wanting a large-screened mobile device that is primarily for entertainment/consumption (without a keyboard in the way). Now you could do everything a smartphone could do, except on a larger screen.
A smartwatch needs to be able to to nearly all of that, without needing any of the others to function. The technology simply isn't there yet.
Wow, that was longer than I had anticipated.