The fact that people are quoting stuff from Cars The Movie in the comments just really goes to show how much of a classic and how influential that movie is and always will be.
The first rulebook for the strictly stock series did cover headlights, they had to be either removed or covered with masking tape. Masking tape was a considerably popular choice, but at some point it became standard to not only remove headlights instead of mask them but cover the hole with a flat plate of metal. It wasn't until the late 80s that teams started to cover the headlight panel with aerodynamic bodywork that removed the distinct headlight shape. How can a NASCAR team get the most basic facts wrong.
We had trouble keeping our headlight decals on even one night on our dirt late model so I got some 1/16th Lexan, cut headlight covers, and used tiny long rivets to pin the headlights and their covers to the plastic nose pieces. After that, the headlights lasted a season or until we had to replace the entire nose piece. Then other racers in touring series saw them, and EVERYBODY started doing it. Great minds think alike, I guess. #51 Matt Furman, Iowa City.
Well thats because of how WEC operates. They mandated headlights because they cant light all of Circuit de la Sarthe (track used for the 24h of Le Mans)