>then surely they would have prevented the mass adoption of always listening, always streaming voice assistant devices

There's something viscerally more creepy about having a camera pointed directly in your face at all times. Try holding your cellphone up to random people at about eye level, you'll see that people do in fact find that at least annoying.

>I think that privacy should be a greater public concern, but I doubt it was the reason why Google Glass failed to catch on.

As I recall, it was the only thing people were talking about.