As a teacher, having the glasses know every student in class and prompting the name for me, to aid in learning all the names alone would make it worth it..
Your comment is already possible with Meta's glass. A couple of students created a facial recognition setup with Meta's glasses. Not just names, but a lot of information about the individual by accessing public data. Given the availability of information, correct and incorrect, via simple searches, this means, as the tech becomes cheap, there no longer is a concept of privacy.
While your use certainly is good, imagine if someone was falsely accused of a crime?
It also becomes a more personal version of license plate readers, where data could voluntarily be fed to law enforcement; or a GooglePerson version of Google Maps. That could help locate missing persons, or a slacker track their victim.