Townhomes already have two-hour fire walls between units. Why do they need sprinklers?

Fire-wall requirements acknowledge that occupants should be spared from a fire caused by their neighbor. But what about the people inside the unit where the fire started? A two-hour separation slows fire from moving to the next unit. It does not slow the fire in the room of origin, which is where most residential fire deaths occur. Sprinklers control that fire in the first minutes, while the occupants are still inside. The rated wall and the sprinkler solve different problems. The one that protects the building is no substitute for the one that protects the family. And the IRC reduces the two-hour wall to one-hour when the townhouse building is sprinklered.