You have to think also about the riders of the different styles of bikes. Mountain Bikes are ridden by big manly men. We need more power to stop all of the huge muscle and manliness we have on a bike. Road riders are scrawny little waifs, they are the starving supermodels of the biking world. Road bikes are light weight and weak, combined with the road riders who are light weight and weak there is no reason for real powerful stopping power. Heck if a road rider were to pull the lever on a disc brake equipped bike it would fling them OTB like a dog shaking a washcloth. Not a pretty sight.
So to answer the questions road bikes don't have disc brakes to protect the road bike riders.
So to answer the questions road bikes don't have disc brakes to protect the road bike riders.
