why did shukhov tell his family to stop sending him parcles?

The guards who open the parcels chop open boxes and pour liquid out of glass containers, and prisoners have to bring bags to carry the contents back in. Prisoners receiving parcels have to give away bits of it to lots of people, including the guard who opens it. Shukhov had received parcels from home while in Ust-Izhma but told his wife not to send him more and take food out of the kids' mouths.