Why is body roll bad?

[HAULN-SS]

Im not much of a road race kinda guy, but I believe it's to keep the tires planted on the track and maintain traction. Body roll around a turn takes weight off the wheels. In Drag racing however, you want a bit of body roll..well, for RWD cars that is, to plant the rear tires and give you a bit of extra traction for better 60' times and whatnot