[Quoth]

In Edit Metadata the Download Cover can search Amazons and other places for covers. It never sets a cover. You pick or cancel.

Amazon often has the wrong cover or a crazy new one for an older book (Publisher stupidity). I often use the Download Cover to find a correct or traditional or older cover for books bought from Amazon. The plugins this uses (Multiple) are widely used so updated when the website(s) change. Who updates your Amazon CMS which can't automatically provide correct covers? The user needs to verify a cover always.

So you are looking for a poorer duplication of something that exists and is more general (but you can disable the searching other sites).

Calibre never sets a cover automatically except at time of adding a book, the cover in the ebook. Amazon does sometimes have totally the wrong cover or product image and sometimes publishers set generic or newer poorer images for covers on Amazon.