The pharmaceutical industry is the very definition of a centralization. It is, after all, an industry predicated on carefully litigated intellectual property, intense de facto regulatory and legal scrutiny, and large-scale, capital-intensive chemical manufacturing infrastructure. As such, it's slow-moving. Drug distribution is thus anticipatory rather than responsive.
This tends to work out at large (epidemiological) scales. But drug needs are not always so macro. Outbreaks are often abrupt and confined; in poor, rural areas, this may mean limited or no access to drugs that may otherwise be facts of life in more developed areas closer and better synced to the pharmaceutical system.