A lot of people do cut it back in the late fall though, and it doesn't seem to hurt anything. Some burn it off in the spring, if they are away from things and fire won't hurt anything else. The main reason for getting rid of the old leaves in the spring is to help reduce the iris borer population. In the other seasons getting rid of the dead leaves helps reduce the moisture around the rhizomes to help reduce the problems with rot. One of my friends cuts it back every fall, and I usually don't. We both have good results.
