Soviet raiders mattered even without many sinkings

Why would Soviet surface raiders matter if they sank relatively few merchant ships?

Their main value was tying down Allied carrier groups, escorts, and supply ships away from the North Atlantic at the opening of a war.

A raider could succeed strategically by creating uncertainty and forcing a response in distant waters. In a short-war scenario, every carrier group diverted south was unavailable for the main North Atlantic campaign. A cruiser also drew escorts and supply ships away with the carrier sent to hunt it. The apparent modesty of individual raiders could therefore conceal a larger force-allocation problem.