If the chassis remains fairly steady then the tires are better able to follow road contours. While springs do an excellent job of smoothing over bumps, they will keep bouncing once started. In other words, the chassis continues swaying and the tires keep hopping long after the vehicle strikes a bump. Left uncontrolled, springs give an uncomfortable ride with very poor tire to road contact. To control this undesirable behavior, a shock absorber keeps the spring from overreacting to every bump or dip and prevent excess movement of the tire and chassis.
Springs are durable items and are easily inspected.
Consumers also often change springs to alter their vehicle's ride and handling characteristics. Spring problems are generally easy to identify. A shock absorbs energy by forcing oil through valves whenever it is moved. It takes a lot of energy to push oil through the valves so when the spring is done pumping, it doesn't have much energy left to keep bouncing. Imagine running 50 yards on bare ground - you could do it and have plenty of energy to run back again.