I just watched about 8 of those Police training videos. Those guys accelerate hard, the brake hard while making a hard turn. Either a right hand ,or a left hand. They're doing circles , figure 8's, and U-turns. And they only use their rear brake.The rear brake provides alot of control and stability in certain conditions. When the new guys use the front brakes mostly from habit, they hit the ground and spend alot of time picking a 750 pound motorcycles. I'm pretty sure using the front brake on a smaller, lighter bike would have the same results. So as far as why anyone would use a rear brake?, there are times when it's the best choice.