Of course I don't need any more dryers, thanks Amazon, I'm good with one, and by suggesting the exact same model to me that I already bought, the only thing you have achieved is rubbing it in that I could have saved almost 100€ had I waited six weeks with my purchase. I'm not exactly sure about the psychological value of this (anyone here who knows whether such actions are of any positive or negative value to a retailer doing it? My gut tells me it's not a good idea to incentivize the user to wait for sales, but that's just my gut...), but there's definitely no use to advertise cloth dryers to someone who just bought one a few weeks ago.
Their algorithms aren't even aware of what the products are, its just "find last 3 things purchased and suggest those."
Just some basic logic could weed out stuff from suggestions - if I buy a fairy princess doll (for a niece) but all my other purchases are tools, computer/electronics, video games, household supplies, etc. then obviously that was a gift or one time type of purchase, even if I shipped it to myself. Don't make suggestions for more fairy princess doll like products because that is the last thing I bought.
I would think they could group users together anonymously and provide trending suggestions based on that. I'm sure there are lots of people with similar sets of categories and they are buying/watching things.
The Netflix Top 10 in the US list is a start in that direction.
Unfortunately Amazon seems more motivated to suggest advertised products (actual advertised ones and ones with inflated fake ratings), their own products and probably stuff they want to get out of warehouses before caring or tracking what a customer is actually interested in.
Them caring about what you want doesn't make them more money.