This happens even with WalMart, BestBuy, and Target though. So it doesn't even need to be vendor neutral. Even within a single vendor they're screwing it up.
Yeah because they are all traditional retailers and have that brick and mortar mentality. They have to pay the "but we have all these properties already" strategy tax every time.
So there's pretty much nobody that can catch up to this level of dominance, not even the second place players. Which is a clear sign that Amazon should be broken up by the government.