It can help to some degree in high-powered, ill-gripping cars and tight circuits (Mission 34 in GT4, but that's off-topic), but that's what rumble strips are good for too, as well as going off-topic.
In MR cars, the redundancy of the emergency brake is even more pronounced, and in RR cars with poor weight distribution... tete-a-queue!
In life, e-brakes are useful in emergencies, as its name suggests, pulling a car harder to run to a complete stop.