Well, but in some cases you did. Many, many items on Amazon are not sold by Amazon. Quite a lot of Amazon's business these days is just acting as a marketplace for independent sellers. This is how they keep an arm's length ("plausible deniability") from the problem. I agree, however, that it doesn't absolve them of responsibility.

But the issue here seems to be that even if you order directly from Amazon or a reputable seller, you could still end up with a product coming from a less reputable seller if it has the same barcode.