Why not? If you said you were going to build roads and put a gas station every 75 km that'd be quite reasonable. You could easily grow a network of stations outward from places that have good infrastructure.
It's do-able, but every additional station adds cost and complication, especially when you're working on the tiny margins and low volumes of developing world drug deliveries in sparsely populated areas. Serving an entire country from the capital (as they probably did in Rwanda) is pretty much the ideal case.