I can see the point of not wanting to routinely drop loads but I don't see any serious danger if proper equipment is being used and I certainly don't see the potential for low g as some are suggesting here.
Also remember that the helicopter itself is not rigidly held in space, it moves when forces are applied to it, and when a shock load happens that shock is not just a function of the weight and velocity of the load and the spring constant of the line but there is also the inertia of the helicopter itself which lets the the load decelerate in a longer distance thereby reducing the max force of the shock load.