Could be, but isn't necessarily.Sure, but it could certainly tie to a fairly common story point. Helping NPC factions defend themselves.
Assuming the story included defending a place. And for it to be a story-driven point, it's not enough that defense is a good idea, it needs to be a story (or at least roleplaying) point.Can also use it to create choke points in many places that PC's can fall back to if they notice a strong force moving toward them. I could find tons of uses for fairly quickly creating minumum of 60ft long 10ft tall walls.