This isn't why disc brakes are popular in the mt bike world. Disc brakes allow more modulation of braking before locking up the tires. If it was all about being able to lock up tires, mt bikers would be running Magura HS-33s with a ground rim.

However, I do agree that disc brakes are not necessary for road biking. I wouldn't give them up on my mountain bikes for anything, but with current tech, there is no way I would ever bother to run them on my road bike.