The sad thing is, facial recognition glasses would be really useful to people like me with prosopagnosia (face blindness), but I would only want them if the processing is done locally on device.
It would be also really useful to have a database of oil company executives and other shitty people that aren't easy to recognize but worth refusing service etc.
Not sure if the trade offs are worth it. It means making up a database of all people. Maybe it could work if your friends and family agree to be in your local database, but not worth it if everyone needs to be in a massive database.