Half the medicine pharmacists administer is poison that does kill some of their patients. Read the side effects -- liver damage, hypertension, death. They know those outcomes are possible and will happen in some percentage of patients.

There is a difference between giving someone poison for no reason, or purely out of malice, vs. doing it because there is some countervailing advantage that justifies the risk. And sometimes the advantage is just that it costs less than an alternative.

People know that an old Ford Mustang isn't as safe as a new Mercedes S-Class, but it's also less expensive.