Pillagers only drop items when killed by a players actions.

I was trying to preform another glitch (reported on it earlier) in which the way Pillagers drop crossbows. when trying to find the fastest way possible to kill the pillagers, i realized that they can only be killed by a player (not sure, just how it appeared)

blocks tested:

arrows from dispenser

lava

witherrose

Way to recreate bug:

Make a killing machine and put pillagers inside, and see if you get any crossbows/emeralds from their drops.