Isn't Perspex or Acrylic just as good?
Polycarbonate windows have many advantages over glass and Perspex alternatives.
Safety is paramount when racing. Polycarbonate windows remove the risk of sharp glass or acrylic/perspex splinters filling the cabin in the unfortunate event of an accident.
Below is a strip of 4mm polycarbonate crushed sideways in a vice. No heat was used to aid bending. Polycarbonate reacts by bending and creasing, demonstrating it's incredible shatter resistance.