Most new motorcycles seem to come with two disc brakes in the front. My bike only has one disc brake in the front and I can easily brake hard enough to make it activate the ABS, thus making my front wheel oscillate between blocking and rolling. If the front wheel is blocking with one brake already, what is the benefit of adding a second brake to it?
Obviously one would need to replace the brake pads and rotors half as often and there is a little redundancy in case one brake caliper fails (but the brake pipe is still intact). But these seem to be rather small benefits.