If a road were perfectly flat, suspensions wouldn't be necessary. But roads are far from flat. Even freshly paved highways have bumps and divots that can interact with the wheels of a car, jogging it up and down.
Without a suspension, those bumps would go right to the frame of the car. The wheels would lose contact with the road, then slam back into the road surface — giving you the comfort-free (and hard-to-steer) ride of a toy wagon. But with a suspension, the body of the car moves forward smoothly while the wheels follow bumps in the road.
Auto suspension has 3 important jobs:
The entire suspension has many parts, including the springs, shocks and/or struts, and their connections to the steering and the chassis. The whole thing has to balance the different jobs of steering and comfort for a given car or truck. A luxury car, like a Lincoln, has a suspension designed for a very soft and cushy ride. So it compromises with less stability in the steering and more body roll. A sporty car will stick to the curve better, but you'll feel bumps in the road more.
The parts of the suspension take a lot of abuse over time — that's their job. So they do wear out eventually. If you have questions about your suspension, bring it into any of our stores for a check up.