That's exactly it, it doesn't hurt them enough that the products they sell are low quality. For every one person that returns a book (which costs Amazon money), there's a dozen that just won't bother, it's not worth the hassle for them.

But there are other platforms out there (especially for books) that people will prefer if they make it easier to find high-quality content. I’m with the poster you replied to; it would make sense for Amazon to go after these fake products.

It's a particularly bad problem for books, but it's a problem for every product category. Unless Amazon sees people abandoning them in large numbers (personally, I haven't ordered from them in years) they're not going to change.