I dunno. I think it's the same issue with Google Glass, AR kits, and Bluetooth headsets. The vast majority of people aren't interested in being quite so openly nerdy as to wear that constantly, and then a lot of the people who do wear it act like douchebags so then nobody else wears it because they don't want to look like douchebags. That happened to Bluetooth headsets- what SHOULD have been an easy 'wear always' thing became a 'I'll act like a douchebag and yell into my headset in public places' thing and then nobody wants to wear one when not on a call lest they be grouped in with the douchebags.

I like the concept of a 2-strap watch/phone, but I don't see it having common appeal. That will also be heavy, and even a basic phone's current weight will be felt a LOT more on the wrist than on the belt / in a pocket. Plus a watch gets exposed to a lot more damage as the user goes about their day so it will need to be a lot better armored (increasing bulk and weight) and also easy to repair.

You may though be right about the device makers wanting us to have two gadgets rather than one...