Maybe because he looks so plain. He looks like a young man...with a headband...and that's about it.
If you pay attention to the debates around Jack the Ripper, it all about why is this person being portrayed as a loli with minimal clothing instead of a mysterious man with a dark persona.
KichiroT said: In the Bible, that's exactly what David did to fell the giant, IIRC.
Nope.
"So it was, when the Philistine arose and came and drew near to meet David, that David hurried and ran toward the army to meet the Philistine. Then David put his hand in his bag and took out a stone, and he slung it and struck the Philistine in his forehead, so that the stone sank into his forehead, and he fell on his face to the earth." 1 Samuel 17:48-49, NKJV
No warning shots, just a single stone hit Goliath. One shot, one kill. They did get the whole "take the target's items" thing correct since right after killing Goliath with the stone, David takes Goliath's sword and cuts off the former owner's head. He then takes Goliath's sword, head, and armor as war trophies.