Maybe to get some extra aggression while driving? More road rage? Honestly I have no idea.
Just take a Halo or cheque drop, a bit safer way to turn into an asshole on the road; as if we don't have enough of them already where I am in TX.

And if you have done this while driving and it was not to save your diabetic ass, you are 100% re-tarded [think Alan from the Hangover].