I think one key factor is that almost no one will expect glasses or sunglasses to also be cameras or video recorders. Consider if you’re in a locker room, and

I think one key factor is that almost no one will expect glasses or sunglasses to also be cameras or video recorders. Consider if you’re in a locker room, and today you see someone with their iPhone aimed at you, there’s a good chance they could be taking a picture or a video. Now you have to be concerned about whether or not their glasses or sunglasses are taking a picture or video of you. It’s a violation of expectation of privacy due to an unexpected new type of “spycam”.