> This is obviously speculation, but I think Amazon could come up with something better if they felt it pressing i.e. recommending the same product category was no better than random products.
You'd think they'd have so much data on buyer behaviour that they could recommend you e.g. other cleaning products that vacuum cleaner buyers tend to buy like mops, dusters and sprays. I can't imagine how recommending you the same thing you just bought over and over that you're not likely to get again for years is going to yield the best results and even manually selected recommendations would do better than that but willing to be convinced as obviously it's in their best interest to be smart here. You'd think you'd even explicitly build in a rule in your recommender system not to recommend something that has been recently bought.
I wonder if the issue is that essentially, nearly everyone buys a vacuum at some point. So, you end up where the only distinct group of vacuum-buyers from whom you can drive recommendation behaviour is people who use Amazon only to buy vacuums, basically you're clustered into either the entire world or a tiny group of Amazon vacuum fanatics.
Another issue might just be that the recommendation engine updates almost immediately, go to the homepage after taking any action (browsing, buying) and it's already updated. So they might've gone for "good enough, but fast" rather than "accurate, but slow"
You'd think they'd have so much data on buyer behaviour that they could recommend you e.g. other cleaning products that vacuum cleaner buyers tend to buy like mops, dusters and sprays. I can't imagine how recommending you the same thing you just bought over and over that you're not likely to get again for years is going to yield the best results and even manually selected recommendations would do better than that but willing to be convinced as obviously it's in their best interest to be smart here. You'd think you'd even explicitly build in a rule in your recommender system not to recommend something that has been recently bought.