Maybe enough people return their fridge right after and buy a new one, or are flipping houses and need to buy multiple washing machines, or are moving into a house with more rooms and new multiple TVs, or decide to buy a mattress as a gift for their parents after buying one for themselves, or any other of the hundreds of events that some exceptional to you or I but happen frequently enough in the aggregate to actually make it a normal enough occurrence to still recommend items that are usually one off purchases.
Or maybe one of the most valuable companies in the world that has gotten to that point largely off of selling us crap is too stupid to realize that people don't usually buy 3 fridges or is unable to hire the talent to tweak the models to reflect this sort of behavior. I've got no firsthand knowledge, but I feel like the former is more likely than the latter.
A/B testing a bad model does nothing. I'm sure Amazon's recommendations are the "best they've got" given their tech. Which sucks.
Google runs a massive recommendation system at scale: their ad placement product (in Search and elsewhere). Google's recommendation tech is astoundingly better than the equivalent at Amazon, rapidly putting the most profitable ads in front of the best potential customers.
That said, Google will never release their ad tech recommendation system "as a service", since it would kill their golden goose. That whole part of their company is a black hole of information.