Riding a bike makes you aware of a lot of things you don't even think about in a car -- cracks in the pavement, grease spots on the exit ramps, dogs charging out at you from the side of the street, the angle of railroad tracks you are about to cross. If people think driving a car is hard, they should try riding a motorcycle. Every curve tries to pull you into the ditch. I've seen riders with decades of experience wander off the highway into the weeds on curves, because their attentions faltered for a few seconds. You have to stay aware all the time.