Piles serve multipurpose functions. When one is building a massive construction project, to lay piles of building materials one needs is handier and a lot faster when needing access to those materials. When I am using a troll to mine a copper deposit, or a golem silver; if I need to make room in my character inventory, making a chest on the spot, to store materials is simply not feasible. Switching to my hammer, then laying piles roundabout is without question the intelligent choice.
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