Amazon is earning a huge profit margin with no liability by letting random entities sell using their website.
Do we want to earn more money too?
Yes.
"Competitor?"
entire board room bursts into laughter
But the reason Amazon probably does not care about that because they have much better profit margin opportunities (AWS, Prime Video and Music, warehouse infrastructure as a service and delivery as a service).
If I buy 3 mule team borax from a Walmart reseller, I have no idea where it is sourced from or how much those entities care about reputation. It could be from 3 mule team, it could be counterfeit.
Think of Rudolph in front of the eight other reindeer :)
But who knows what is happening behind the scenes. Amazon removed the wording that made it clear they commingled inventory, but I am sure they still do.