I won't use an eyeglass mounted mirror for the simple reason that I wear expensive prescriptions. Ir the mirror hits something. I do not want my glasses damaged (and I have learned the hard way that impacts to glasses frames hurt! Bridges of noses were simply not made to take that abuse.
Yes, those impacts usually happen around the house. Open cupboard doors, projects in my shop, etc. Doesn't matter to me where. I consider my glasses a high priority. (And several hundred dollars, a week's wait and two trips to the eyeglass people with the first being quite expensive if it's been more than two years since my last prescription.)
If I crash to that side and lay my helmet down, mirror is dying wherever it's mounted. But I get to chose what it tries to destroy as it is twisted off its mounting point. Helmets don't care. Eyeglasses do.