Except it's harder to unobtrusively check a necklace to see if you can ignore that message and not interrupt your lunch/dinner conversation. And a watch and a bracelet are the same thing (e.g. a wristwatch is a bracelet that tells time) and they consume the same space. A cufflinks or a sleeve button will only work on long sleeve shirts. The google glass thing is so far a failure, but maybe eventually will morph into something more acceptable socially and at work, or people will implant them into their eyeballs. A ring is another possibility, buy most men only will wear a wedding ring and only if married.
You seem to be trying to justify the watch. The point of these examples is that there will a myriad of options for all the reasons people may want to use a smart wearable. I could give a flip about notifications for instance. Moreover, all of these obstacles will be overcome, in much the same way that technological advancements in just a few short years have made the Watch possible. The simplest solution is a display in a person's current glasses. Slightly more complicated would be a contact lense. But Siri is the key. Did you see HER? You won't need a display. A simple earpiece hidden discreetly like a high end hearing aide will be all anyone needs to receive unobtrusive notifications. This technology exists today. Siri unfortunately isn't up to the task of being the sole interface, so Apple was forced to include the ridiculously tiny 1" display forcing people to squint it at -- hardly unobtrusive -- people notice when you look at your watch, no matter what you may think. Engaging in a series of flicks and reading information is going to like waving a red flag to your company. A whisper in your ear wouldn't be perceived by anyone. That's the future of wearables, and I suspect it will be here long before smart watches put the Swiss watch industry out of business.