Why do many countries ban the sale of one's own blood?
According to this article, (in Spanish) blood from people recovered from covid-19 is a millionaire's business, laboratories in the US were paying up to thousands of dollars for blood from people who had recovered from Covid-19.
According to this other article (also in Spanish), blood was being sold for 3,000 dollars in Bolivia, but in that country, selling blood is illegal, because it's considering "trafficking".
And in Argentina, a proposal to pay people who recovered from Covid-19 for their blood never happened.
I have a friend who lost his job due to covid-19 (the business he worked in closed because sales went down), and now he can't pay the rent, if he could sell his own blood to a private clinic or lab or something, that could save him from the bad moment he's going through.
What's the logic behind banning the sale of one's own blood in several countries?