Windshields have not always been "shatter proof". In 1890's auto glass was ordinary glass, and in the event of impact the glass would shatter into sharp fragments causing sever injuries and death.
In 1905, Eduardo Benedictus introduced laminated glass which consists of two layers of glass with a layer of polyvinyl butyral (PVB) sandwiched in between.
Windshield replacement has become more difficult as there are ADAS cameras, lasers and sensors that have be calibrated. OEM auto glass is still preferred by all major insurance companies.
