Cruise control helps because it maintains speed. Where as a lazy foot would reach speed, let off the gas completely, and then accel again when the speed drops. It takes a lot less force to maintain speed then to accel. Cruise Control can be bad sometimes because it lacks the intelligence to slow down for bends and speed up before hills. It is also boring because it lacks the thrill-seeking to accel quickly for little bumps for that brief sensation of weightlessness. It also lacks responsibility to pay for speeding tickets! >:O
Cruise Control can waste gas if you "resume" it after slowing down. You should get your speed back up manually, then "resume" it. Cruise Control is just meant to maintain speeds, not neccessarily accelerate to them.