By constantly changing a skeleton's offhand item with a repeating command block, it makes the skeleton's behaviour very strange. They would never attack you even if their bows were fully charged, and would constantly follow you instead of strafing.

How To Reproduce

1. Get a skeleton.
2. Input this command "replaceitem entity @e[type=minecraft:skeleton] weapon.offhand minecraft:whatever_item_you_choose_including_air" into a repeating command block and set it to "Always Active".
3. Go into survival mode.
4. Observe how the skeleton would charge up their bow, but never shoot you. They would also try to run into your position instead of keeping a distance away from you and strafing.