Nobody disagrees with commingling in theory, but, the problem is you have some bad actors who will pollute the communal product bins. It is not obvious who they are because there is no tracking of individual items, only by ASIN.

Tracking by (ASIN,UUID) pair would at least allow them to figure out who the bad actors are and flag/pull those items.

There are lots of things they could do to try and help. The problem really is, there is no incentive for Amazon to do any of them.