Because it is beyond inhumane and so unimaginably ethically wrong to test POISONOUS, addictive substances on these innocent sentient non-human beings who would never on their own decide to suffer these agonies. HUMAN BEINGS, on the other hand, engage in this dangerous and addictive activity COMPLETEY of their own volition. Their own CHOICE. It is obviously NOT needed for life; it actually tends to have the opposite effect. Any person that can subject another being to these horrors is acting in intolerable and sadistic manners.