Durability would hardly limit the applications, the vast majority of optical coatings are inside things like camera lenses. Glass is a sensitive thing after all

Durability would hardly limit the applications, the vast majority of optical coatings are inside things like camera lenses. Glass is a sensitive thing after all anyway. They don't put any of the sensitive coatings on the front element, it's essentially a glass covering these days. Eyeglasses are the only optics I can even think of that are regularly damaged and in contact with various hazards that can't really easily be shielded.