I could see three reasons really. One would be the fact that you can keep your revs up at a drag strip launch simply by just slipping the clutch don't now really how the smg's or what not work but i couldn't see having this kind of control over rpms via clutch. Two would be clutch dump burnouts. Nothing better than just revving the car up to 5 grand and dumping the clutch. Three would be drifting w/ clutch control....Can you tell I break alot of stuff. Good thing for warranties.
One question though on those how does it work taking off from a stop with the clutches or what not. I never have really got much exposure to these.