3-4 degrees negative camber helps put the tread flat on the ground when under side load. Under load, the tire's carcass wants to flex and lift the inside of the tread off the ground. Also as the car rolls, it wants to tip the tire to where the inside of the tread is being lifted off the ground. The car’s suspension geometry tries to make up for some of this but it cannot totally compensate. Running negative camber compensates for this. By keeping the tread on the ground you get better front grip and less understeer. You don’t want your drift car to understeer if you can help it. If your car has multilink front suspension, you can use closer to 3 degrees of negative camber, strut type suspension can use closer to 4 degrees. Don’t run crazy amounts of negative camber, like demon camber hellaflush style, it’s going to hamper your front grip.