With drums, if you break an axle, it can come out and tear up the side of your car. Rear discs will hold it in place, so you can feel a little more confident about launching harder. They do more than just stop, they act like C-clip eliminators on the part of keeping the axle from popping out - without the leaks from C-clip eliminators.
"Racing is life. Anything before or after is just waiting." - Steve McQueen