This completely takes away the responsibility of throttle control. Without it, any heavy handedness with the throttle can cause your drive wheels to lose traction and start spinning and smoking. If left spinning for long enough, the cars can start to donut (spinning on the spot), throwing you in a random direction, sometimes in the opposite direction to your competitors! This problem is worse if you're wheel spinning whilst going around a corner. Because there's more yaw momentum (turning force) your car could flip out even more.

Traction control also helps out if you come off at a corner. Invariably, you end up in grass or gravel, which gives you less tyre grip. Again Traction control will help you out by providing just enough power to get back onto the road.