Their incomes, their physical safety, and indeed their very lives are endangered by the law. The war on drugs is actually a war against drug traders. The faint of heart would quickly retire from the battle. The more ferocious ones would choose instead to defend themselves. And if the people who were warring with them had guns, as our police officers do, then it follows as day follows night that the combatants on the outlaw side of the war would have to arm themselves too.
Wars usually result in some civilian casualties.
The war on drugs is no different. The resemblance to real war goes further still. In the war on drugs, police have the same problem that American soldiers had in Vietnam. The enemy-drug traffickers are visually indistinguishable from the rest of the population. So the conflict becomes a guerrilla war in which everyone is a suspect.