Mobs don't drop equipped items when killed with projectiles

My bow has: Power IV, Unbreaking III, Punch II, Infinity I (NOT Flame): when I kill mobs they drop any natural drops (bones/arrows for skeles), but never items (swords, armor, etc.). With my sword (w/out looting) everything drops at normal rates. Tested with 50 skeles on creative, zero item drops (but normal bones, arrows, etc.). Same with Pigmen, Zombies, etc.