Why is America Still Speeding?

Since gas prices have shot up, I have been determined to be less of a lead foot and conserve gas. Let's face it, driving faster than 55 mph causes a significant increase in gas consumption. Efficiency drops 7% to 23% for every 5 mph over 60 mph. So why, I ask you, do cars drive past me like I am standing still? In my time wasting blog wanderings this AM (ahem), I saw someone asking for a bumper sticker that said, "Get off my ass, I'm saving gas". I need that one.