why do racing cars have very wide tires?
Moreover, the tires must be able to support much larger loads than the weight of the car which is also helped by the larger tire area.
Wider tires provide more resistance to slippery spots or grip on the road. Race tracks have gravel, dust, rubber beads and oil on them in spots that limit traction. By covering a larger width, the tires can handle small problems like that better.
Wider tires have improved wear characteristics. In order to achive maximum traction, the tires are made with materials that ablate as the car runs through the race - which is why the tires get switched so often. Narrower tires would wear out more quickly.