When I buy a widget from Amazon, I'm not actually getting a widget from some particular merchant on Amazon.

I'm getting a widget that was pulled out of a co-mingled inventory box at some Amazon warehouse.

Amazon owns the entire shopping experience, end-to-end. They run the website. They design the website. They handle payments. They advertise the items ("Customers who bought Foo also bought Bar"). They handle shipping. They handle refunds. They handle warehousing.

But they don't seem to want to own the responsibility. I'm assuming that's because it's not the profitable part of this equation.