The United States is the grandmaster of high tech weaponry. We have killer robot planes flown by nerds thousands of miles away from the actual fighting, computerized grenade launchers that can shoot round corners, and a new jet (the F-35) whose development cost exceeds the gross national product of Columbia.
But cheap works too if it is matched with ingenuity.
The patrol would have to call in a helicopter evac, revealing their position so the Viet Cong could either organize an ambush or just melt into the jungle. There were no metal parts for detection equipment to find, no explosives for sniffer dogs to spot, and they maimed which is more disruptive to an American military unit than killing. They were the perfect booby trap.
Probably the most effective use of wooden cannon were the Quaker Guns. During the American Revolution, a company of 125 Loyalists were barricaded in a home. Americans tasked with rooting out the Loyalists built a fake log cannon and threatened to bombard the house unless those inside surrendered. Faced with what looked like real artillery, the Loyalists surrendered without a fight.