As with all products on the market today, cars are built to a certain price point so that they are competitive in their target segment but at the same time produce the maximum profit for the manufacturer. And in building these cars, the manufacturer cannot scrimp on the easily visible things like interiors, accessories or wheels. What they will scrimp on is in the components owner do not normally check, like stamped steel suspension components or substandard shock absorbers.
Most especially with mid-priced and entry-level cars, the components that will be compromised are internal engine components (cast vs. forged parts) and suspension components (stamped steel vs. forged lighter weight parts and cheap OEM shock absorbers). Luxury cars and sports have few compromises in this regards, but this is why you pay top dollar for them. Still, there is a thriving market for even this segment because aftermarket shock absorbers, springs and other suspension components are still sought after by owners who are setting up their cars for autocross or track use, for example. When a vehicle is modified towards a specialized use, the focus becomes geared toward a particular performance aspect of the car, and factory compromises geared towards the 80th or 90th percentile of the population are thrown out the window.
Plenty of people will argue that their cars ride and drive excellently, and this will be true of newer cars. But cars that are driven often on bumpy roads will necessarily suffer from more wear and tear in their suspensions compared to cars that are driven on smooth roads. This is where the difference between good aftermarket shock absorbers and substandard shocks will become evident. Even new, substandard OEM shocks will suffer from fade much faster than high performance ones. Because of the constant up and down movement of a shock as it dampens suspension movements, the oil inside the shock will heat up. Cheap shocks will have oil that loses its viscosity with the heat and even foam inside the shock itself. Studies have determined that when this happens, up to 35% of the shock's performance will degrade. Aftermarket shocks are built to a higher standard, such as having aluminium bodies, nitrogen pressurization and higher quality oils so that this fading is minimized. A lot of aftermarket shock absorbers also offer compression and rebound damping so that the vehicle's handling can be fine-tuned by the owner. Finally, the best aftermarket shock absorbers have lifetime warranties, so even if they are initially more expensive, these aftermarket shocks will last the life of your car while giving consistent and reliable performance in all conditions.