Answer:
Having bacteria would produce organic molecules and defeat the whole purpose of the experiment which is to make organic molecules from inorganic molecules. The experiment was supposed to demonstrate the formation of the first organic molecules that initiated life on primordial earth. It is believed that lightning powered the formation of the first simple amino acids, like glycine, from the primordial atmosphere which was mainly composed of carbon dioxide and methane.
The earth will have lack of oxygen and the earth's temperature will increase in heat rapidly.
Plant cells have cell walls while animal cells don't
I believe that the disadvantages outway the advantages. Afterall we want to stay healthy and live longer.