Bats don't drop items they are holding in Minecraft

I was trying to make bats drop items when you kill them by equipping them in their armor or weapon slot, but when I killed them they didn't drop the item. I tried using /give and /replaceitem but it didn't work. Here are the commands I tried:

/replaceitem entity @e[type=bat] slot.weapon.mainhand
minecraft:feather 1 0 {HideFlags:5,Unbreakable:1,display:{Name:"Bat
Fang"},ench:[{id:16,lvl:1}]}

/replaceitem entity @e[type=bat] slot.armor.head minecraft:feather 1 0
{HideFlags:5,Unbreakable:1,display:{Name:"Bat
Fang"},ench:[{id:16,lvl:1}]}

/give @e[type=bat] minecraft:feather 1 0 {HideFlags:5,Unbreakable:1,display:{Name:"BatFang"},ench:[{id:16,lvl:1}]}

All of the commands were successful but when I killed the bat, it didn't drop anything. I tried it with other mobs and they dropped the item. Why does this not work with bats?

Check the bat's drop-rate on those slots. I believe by default they are all 0 because they never have those slots equipped.