Because clay blocks fill less in inv than balls, so I don't have to run back and forth a lot when hunting wild clay.
So I'll have to place it somewhere to shovel it again, and the best option for that would be infrastructure constructed for the purpose instead of in a random location. In the future, there will be rails with storage carts at the clay tank so it can be transported quicker to the forge (I think), and there will definitely be cargo rails from the forge to the public storage.