In Micah and Isaiah, spears are bent into pruning-hooks and swords into plowshares, but in Joel they are bent back.
I guess they didn’t have enough metal to maintain a reasonable inventory of both.
These days, we’ve got lots of metal, but it’s always good to recycle.
Plus, who really needs plow-shares or pruning-hooks these days? Instead of bending swords and spears into them, you can make good money selling weaponry to some Renaissance festival role-player.
Sure, you might need to dull the edges a bit or encase them in a hard resin for safety, but that’s easier than bending.