When you put a brake on the front hub, you have to make the fork really strong. Rim brakes allow a lighter, springier fork. That's why disk brakes and drum brakes, developed in the 30's and 40's, never became popular. But in cycling, everything that is old will sooner or later be new again, and now disk brakes are all the rage again. They stop really well. Unfortunately they have side effects, such as stiff and uncomfortable forks.