@Talh
If Yuusha ga Shinda is any hint, traps only serve to slow down the enemy while at the same time, be inconvenient and dangerous to civilians. irl, we have innocent people stepping on mines during peacetime. you don't want to fill the forests with traps only to have adventurers and travelers get caught in them.
A manned wall is always better than multitude of traps, and a wall will even stop horses. Traps are only better than walls if you don't have enough people to cover the walls.
However, they're up against apparently what was called a
horde. Yeah, I've read Goblin Slayer (the manga); for the most part, the goblins raiding villages are usually all part of one tribe (much smaller than a horde). The goblins here are all under a
queen.
Also, Orcbolg is crazy. He actually wouldn't need that many traps for one village if the people of the world he is in takes goblins really seriously.