Why is there no talk of lowering the speed limit to conserve gasoline?

Is it because we live in such a stupid nation that it would cost bazillions of dollars to send legions of trucks out to change all the signs, or because of the dire need of fat morons to get through Wyoming and Nevada at 75 mph (posted, actually they do like 90 in the biggest boxiest pickups and SUV's you can get). I mean, if you ever find yourself in Wyoming or Montana, of course you'd want to do like 120 mph getting the hell out unless you own smelly refineries or hunt cougars, but what, are there important people there that haven't heard of telecommuting yet? Is the thinking that if enough people get killed on the highway, there'll be more gas to go around?