>>1365763Under maximum front braking, your rear wheel has almost no traction and is about to lift off the ground. You brace yourself against the bars, and ride that line. If you use your back brake, the rear wheel simply locks up immediately and skids. It does not contribute to braking at all. If your rear wheel is not skidding under emergency braking, your front brake is not powerful enough or you're not using it hard enough. What part of this don't you understand?
Cars weigh like a tonne and their center of gravity is much lower.