> Actually, though, most people don't need to lock their car doors nearly as much as they think they do. About 1/3 of cars that get stolen are stolen because the driver was stupid enough to leave the keys in the ignition.

True, but why make it easier? Plus it's not always about stealing the car itself, but what's in it. A lock adds at least a little difficulty and time to getting inside and that's often enough to curb temptation in today's instant gratification society.