This sounds like cross-shipping, where you ship to a distribution centre which then ships to the final destination. My guess is that this is more expensive and slower for a lot of cases (this is typically cheaper for extremely high volumes or cross-continental shipping).

Shops with which I’ve worked will have several different carriers pick up packages during the week. Some pickups are for city-local packages, where others are cross-province packages. Finally, lots of packages are delivered from the shop directly by motorbike. The logistics are quite different for each, and they use different providers depending on situation.

Shipping everything to one location that redistributes would explode in both costs and complexity.