I don't know whether an attic is any more likely to catch on fire than another part of your house, but the attic is a place where a fire can get out of control in a hurry.
A family in our neighborhood was burned out of there home when a fire started in the attic and quickly spread. The family members said they heard the smoke detector in the attic sound, and they were going up to see what was causing it to go off. Like most people would, they assumed it was malfunctioning, but they still went to check immediately.
By the time the husband got half way up the pull-down attic stairs, the fire was already too hot and had spread too much for him to go any farther. Fortunately, the entire family got out of the house safely.
They later learned that the fire was sparked by an exposed wire, and the reason it spread so quickly was because of all of the newspapers, and other old papers and fabrics stored up there. There were also a lot of cardboard boxes. And once these items began to burn it was only a matter of time before the fire retardant insulation burst into flames as well.