Conflict is expensive. People die and it gets messy. There is a "peace dividend" (Steven Pinker explains it here) which opposing parts can gain if they cooperate with each other and trust one another. The division of labor helps promote cooperation and trust.
High homicide rates in Latin America is partially explained by conflict among drug cartels and its effects. Drug prohibition in Latin America limits the division of labor, reduces cooperation, and lowers trust (Adam Smith). Eliminating (or reducing) prohibitions can make peace more valuable than conflict. For selfish reasons.
See more on the relation "division of labor" --> "cooperation" --> and "trust" in this review of Paul Seabright's book The Company of Estrangers, in the section "evolutionary affairs."