Extra small feature for some of those, usually older, cars with highly refractive headlights. There are a lot of beautiful models, but with original AC shaders headlights do look a bit upsetting. This addition helps headlights look more natural and it doesn’t add any passive costs (unlike some post-processing effect would), and is pretty cheap to calculate in general.
In this video:
• Caterham 7 Super Sprint by Ben O’Bro and JackCY: