Because they look cool right! The performance benefits of custom wheels should be your answer. In the 1950s and 1960s race car drivers developed lighter magnesium wheels to reduce weight and enhance performance in all form of racing. They were called Mags by the racers, a term still widely used today. However, most magnesium wheels were far to fragile for daily street use. Plus magnesium oxidizes very quickly and require frequent polishing. Magnesium wheels used in modern race cars are often forged to make them stronger and reduce weight. As a result contemporary forged magnesium custom wheels are very expensive. The oxidization problem is the reason you don’t see contemporary custom wheels made of magnesium.
Fortunately for the custom wheel market today manufacturers developed light weight aluminum alloy wheels that provide the strength needed and come in numerous finish options while reducing wheel weight. Trendy wheel finishes include chrome and polished aluminum, plus painted aluminum alloy come in hyper-silver, silver, white, black, gray and Anthracite. While many of us choose aftermarket custom wheels for their good looks, there are many important performance benefits resulting from reducing a wheels weight compared to factory steel wheels.