A lens is a true marvel! It consists of a material that has to be perfectly clear: transparent, pure, clear, and homogenous in the structure. And it requires a material that provides the highest precision in manufacturing and processing. It should provide UV protection even without tinting, and be easy to care for.
Plastic lenses are lightweights and that way ensure high wearing comfort. Special coatings like Rodenstock Solitaire® Protect Plus 2 prevent reflections and protect the lenses against scratches.
Quite a few glasses wearers still swear by tried and proven mineral glass. Even though glass seems to be very fragile, it is astonishingly stable and resilient. The low care requirements and high scratch resistance are advantages over plastic lenses. Many glasses wearer simply accept the somewhat higher weight.