It has the added benefit of having a high probability that you'll be interested in the product, since you wouldn't be on the page if you didn't find the topic interesting. Instead we get tracking networks showing you ads for TVs because you bought a TV last week.

I think the problem with that is that most browsing is done on pages that do not target a valuable topic: news, weather, memes, etc.

For that reason, it's better to remind you about that Amazon product still in your cart while you're browsing for random stuff.

I used to to that with Amazon. About a decade ago, I added an Amazon banner, and the link included a search term. So I would add an appropriate search term (related to the top blog entry on the page, which is where the Amazon banner appeared). Sometime in the past few months, Amazon removed that and only allows generic sales banners to be presented.

Considering the sprawl of sponsored content, maybe because it's cheaper/easier to just buy the author?