It's because the Looting enchantment will only occur if the item is in your Main Hand. It can only work by using commands to modify the item. As proof, hover your cusuor over your item and it should say 'When in Main Hand:" and the damage from the item (as I don't know what type of sword you're using) and it's enchantment. By using the commands by using {Slot:"offhand"} in the command, then the looting will work. Sadly this doesn't work without cheats enabled on survival 😞
Evidence of the world not crashing. The second image has proof that I am on a 1.9 World.
This is not an error with Minecraft, just your computer. I have VBO off and I can still assess 1.9 worlds. If I could, I would sent a screenshot showing I am on a 1.9 world (by the Attack Interactor tag) with the VBO off, but the world isn't crashing.
Alright, thank you for your information.