When I think of smart glasses, I imagine the best possible version of them as an exercise in thought. It starts off with them being in a form factor that's effectively indistinguishable from "normal" glasses. After that, I imagine them having the processing power to provide full AR capabilities, as well as a battery that's able to sustain that technology for at least a day if not longer.
I suppose that in turn might make you ask, "What is 'full AR'?" For the sake of this I'm going to imagine a world where there are no nefarious actors or ill-intentions. This is a fantasy world where I can just geek out over cool tech.
To me, it's the ability to recognize any and all people you interact with, at a moment's notice. Think all social media networks combined, but in realtime, as soon as you lock eyes with a person. The ability to "remember" a person you met ten years ago at that one networking event is now possible. Extrapolating this into other social spheres, you could get rid of all of the traditional dating apps that exist on your cell. If you walk into a bar or [$genericSocialSetting], you can immediately see who is single, and who isn't (assuming they have this information broadcast). Dating just got significantly easier, and maybe a bit more organic since you can tell right off the bat who is looking (and maybe even see if you have something in common).
Looking into other areas of use, imagine having Wikipedia at your finger tips, overlain in your field of vision. I'm not talking paragraphs of text here, but rather some sort of intuitive UI that cleverly displays the most significant bits of information about a given object, place, person, etc, within your field of vision. "That plant is poisonous."
Smart glasses represent taking all of the data and information that's available on the internet, and overlaying it in the real world. The "killer app" for smart glasses is several years out, and it will take many iterations before it's perfected. They're going to augment how we function, just how smart phones have augmented us. You'll be able to record, snapshot, and replay scenes from your past just like you can do with your phone, but far more effortlessly. I can imagine a world where your smart glasses are constantly recording, but only choosing to "save" given your input (since a lot of moments we wish we could have saved happen without us having our phones out.) Again this is pretending we live in world with zero nefarious actors (Black Mirror does a good job of covering some potential negatives of tech like this).
I think we're a long, long ways off from this tech. It's going to be a big culture shift in many ways, and is going to happen slowly at first. In my mind this is the sort of thing that Thalmic, Magic Leap and others are pursuing. I see companies like that as the early Ford Motor Company. These early Smart Glasses/AR companies are producing the Model T. Our smart phones are the "faster horses" in this analogy.