Initially, body kits (formerly known and sometimes referred to as ground effects) were produced as a result of the need to reduce drag on racing vehicles. The idea was that the ground effects would lower the profile of the car, and create less wind resistance, or more efficient aerodynamics. This worked by deflecting the air to travel around the car instead of underneath it. Furthermore, with the improved aerodynamics, the car became easier to control as it reduced lifting effect at high speeds.
A man known as Jim Hall was one of the first scientific pioneers to experiment with car aerodynamics. Prior to Mr. Hall's place in history, aerodynamics had been engineered mostly for the use of aircraft. Hall's ideas and projects began in the start of 1961, however, the benefits of his improved, aerodynamic designs were not discovered until much later. In 1970, he eventually helped manufacture a car to compete in the Formula One races. Unfortunately, however, Formula One banned the use of these "aerodynamic cars" that same year, as they were believed to have an unfair advantage.
After Hall, other aerodynamicists and designers took stage attempting to produce a car similar to what Hall had envisioned. Some notable contributors included Gordon Murry, Peter Wright, and Tony Rudd, amongst others. Eventually these aerodynamic cars were allowed back on the race track, however, a well known racer known as Gilles Villeneuve, died in a horrific car accident from a similar (aerodynamic) vehicle. As a result, the design was again banned on the race track in an effort to keep vehicles at limited speeds.
Despite these events, car enthusiasts have still continued to improve on the aerodynamics of their vehicles. Whether they are looking to improve the styling and exterior appearance (with body kits) or attain benefit from the improved performance of an aerodynamic vehicle, it seems to work.