People should be encouraged to donate blood

JOURNALISTS FROM BEIJING NEWS found that in a hospital in Yanjiao, a town in Hebei province, there is an illegal network selling blood. Patients who need a blood transfusion have to pay agents. They then organize people to sell their blood to the patients. The newspaper comments:

The Law on Blood Donation clearly states that blood donations without compensation are the legal way of obtaining blood. It also unambiguously prohibits the selling of blood. Those organizing the selling of blood face legal penalties and even criminal charges.

Yet the illegal selling of blood has never totally disappeared. A browse at past reports shows that the authorities have launched repeated campaigns against those selling blood. Yet they still exist. Why?