Why Allied surface raiders found little Japanese trade to interdict

Why was surface-ship trade interdiction against Japan not pursued even late in the war?

When suitable forces finally arrived, little trade remained to attack, and sanctions had already reduced the wartime economic shock.

Commerce warfare requires a continuing flow of targets, and little Japanese trade remained once Allied surface forces could reach the routes in strength. That scarcity followed the sanctions imposed before the Pacific War. Cutting trade in peacetime can force the target economy to begin adapting before wartime blockade starts. This helps explain British caution toward some American sanctions: an immediate economic shock during war might be more disruptive than a restriction whose effects had already been absorbed.