I suspect that the robbing chit has been raised to highlight critical spares shortages and account for the costs of spares shortages. A rise in the incidence of robbing is often the first sign that the supply system has a problem. Previously, the loggies had to rely on anecdotal evidence to know that this was occurring at the front line.
Additionaly, robbing carries a cost in manpower and equipment, as you now have to repair 2 items, the U/S one and the donor.
Retard