because everybody is in a big fcking hurry to get where they have to go. reality of it is that they really dont get there that much faster. people are always in such a rush. if im driving down a state highway in the middle of nowhere and nobodys behind me i do 55. saves alot of gas. people are in a hurry to get nowhere fast. pisses me off when someones tailgating me when im already speeding. then they get to kiss my ass when i slam on the brakes.